How to automatic mixing water

[Coleus]

Well, i am thinking of a process to mixing my fresh salt water automatically so i can have auto waterchange.

I have salinity probe, float switch and outlet controls so i can turn on and off outlet when it meet the salinity. My only puzzle is how i can find some kind of rotating drum (just like a fish feeder), that can slowly pour the salt into the water bucket until it reach the salinity level. Anyone know one that is bigger enough to do the job?

[hillegom]

you might also think of something with an auger, like the pellet stoves use. However, it would have to be made all out of plastic.

[michika]

Auger seems to be the best option, and I can tell you because I've spent two years now looking at and for really well done automatic water change systems. There aren't a lot out there yet.

If you want some other ideas there have been people who have automated the process using their Reef Keeper controller on the Digitial Aquatics forum. Even if you don't have an RKE, some of the styles and problem solving techniques might be worth it for you.

*Edit* While I was looking for something else this thread on RC popped up about different mixing stations. I know they aren't all automated or anything, but it might give you some more ideas. Salt Water Mixing Stations Let's See Them (http://www.reefcentral.com/forums/showthread.php?t=1711626)

[Cranky When Wet]

Rotating drums immediately brings to my bunny mind a Lapidary tool.
:laluot_23:
Lapidary is the art of cutting rough rock into gem stones. Normally, rotating/grinding machines are used for the process.

A less-formal method involves using various sizes of rotating, plastic-lined, drums for polishing rock.... it's a good method for teaching kids how to polish semi-precious gems since the machines are much safer.

Drums can range from one pound capacity to any size you want (i.e. 10, 20, and commercial sizes beyond that).

The trick will be to automate how the salt is dispersed.

I suggest speaking with the Calgary Rock and Lapidary Club. They could direct you to people who could help you see these units in operation and even to buy a machine if someone is no longer using theirs... Here's the link: http://www.crlc.ca/index.htm

Hope this helps and will look forward to hearing your success :-)

Bunny

[Lampshade]

The issue with drums is finding a food safe drum so that the Bearings aren't exposed to the salt, and also made of stainless. Anything else would be pretty scary to use on the tank :S.

My opinion would be a simple hopper with a valve. You need something that will seal off the salt when not in use, if it's in the same area as mixing water, the humidity will make it a salt block in no time. If you made a desenct sized hopper with a small outlet, even a 0.5" opening you could open/close that to add salt. Program it so that the hopper is open for a short period then closed for 20+ seconds to allow the salt to mix. Make it cycle whilever your salinity is low.

[Cranky When Wet]

All very valid points...

With that in mind, Lapidary tumbler drums are typically isolated from bearings... I wish I could comment on the grade of the poly/vinyl liners but I've never tested the units for SW applications.

There are a number of manufacturers worth speaking with i.e. Thumlers, Covington or Lortone (just don't look at the cheap units - they are trash and don't last.)

Covington does make a "Hopper-type" unit for polishing gold/silver castings... Here's a link to see what they look like...
http://www.covington-engineering.com/deluxe_tumblers.htm

One might look at their "Vibratory" Tumblers as well? Tho I'd be concerned about heavier elements sinking to bottom and causing tank troubles... http://www.covington-engineering.com/vibrating_tumbler.htm

I'd personally lean towards Covington for getting answers to technical questions...

I do like your thoughts on using a hopper sporadically :-)

Bunny





The issue with drums is finding a food safe drum so that the Bearings aren't exposed to the salt, and also made of stainless. Anything else would be pretty scary to use on the tank :S.

My opinion would be a simple hopper with a valve. You need something that will seal off the salt when not in use, if it's in the same area as mixing water, the humidity will make it a salt block in no time. If you made a desenct sized hopper with a small outlet, even a 0.5" opening you could open/close that to add salt. Program it so that the hopper is open for a short period then closed for 20+ seconds to allow the salt to mix. Make it cycle whilever your salinity is low.

[sphelps]

Super saturation is your answer. Setup another water top off using something like a 29 gallon aquarium. Drill and install an overflow in the aquarium and mount the aquarium above sump level. From your fresh water top off use another pump or solenoid depending how it is setup. Send one fresh water line directly to the sump (Fresh top off). Send the other fresh water line to the 29 gallon aquarium (salt water top off). Plumb the overflow into the sump so when fresh water is added to the 29 gallon it overflows and drains into the sump. Next fill the 29 gallon with water and add a full bucket of salt, use a small powerhead to keep the water circulating and even a heater if you wish. Now setup your controller to either activate the fresh water or saltwater top off based on the salinity measurement in the sump. The salt water added will be supersaturated but it won’t matter as the controller will simply cut it off once salinity is restored in the sump. This will maintain salinity so to auto change water simply hock up a pump and timer in your sump to pump water to a drain. Depending on the controller you can even set an alarm for low salinity which will prevent the pump from removing water so it won’t change water if salt is needed. And when salt is needed simply add another bucket to the tank, doesn’t get any easier. Done this exact system with a profilux before, it was dope!

[russp]

I may have an idea for you , I own a convenience store & I have a hot chocolate machine that has a food grade plastic hopper with a plastic auger in the bottom . It is driven from the back by an electiric motor & coupler system. the hopper would probably hold about 2-3 lbs of salt at a time . I will try to post a picture for you if interested.

[Bloodasp]

Problem with supersaturated solution idea is the amount of maintenance you have to do to the ATO pump. As It doesn't run continously so if the water evaporates your ATO will eventually clog with salt pretty fast since it is supersaturated.
I'd go with the auger idea, just what type of material it should be made of would be the issue, plastic wouldn't work as the salt would act like a sandpaper and would wear the auger out in no time.

[Bloodasp]

Though I wonder if an auger made out of PVC material would work.

[golf nut]

I do like the supersaturated method but was warned against it for some reason when I posed a similar question, I will need to dig up the thread that is out there someplace.

A plastic auger wouldn't be that hard to manufacture, what size do you want?

[russp]

Here are a couple of pics of the hopper I was talking about . Not great but I think you can get the idea.http://i966.photobucket.com/albums/ae141/russp6299/P1050144.jpg

[Coleus]

Thanks russp, but I am looking for something that i can just buy because i am not that handy man that can make things :-) SAD

[sphelps]

Problem with supersaturated solution idea is the amount of maintenance you have to do to the ATO pump. As It doesn't run continously so if the water evaporates your ATO will eventually clog with salt pretty fast since it is supersaturated.
I'd go with the auger idea, just what type of material it should be made of would be the issue, plastic wouldn't work as the salt would act like a sandpaper and would wear the auger out in no time.
Actually the way I described it this could not happen. The salt water top off pump will only pump fresh water into a tank and then the saturated salt water overflows into a drain that goes to the sump. If you made the drain at least 1/2" there's no way it would clog, plus it's a drain and will be empty unless the top off is running.

Like I said this system was used on a reef tank for about a year before the entire system was sold off. No problems occurred during this time. A hopper system isn't really going to work as well as one might hope, it will cost more and can clog up if the salt is exposed to air. Ever left your salt bucket lid off before and ended up with salt bricks? Same deal. Even straight out of the box or bucket salt is often clumpy.

[sphelps]

I do like the supersaturated method but was warned against it for some reason when I posed a similar question, I will need to dig up the thread that is out there someplace.

A plastic auger wouldn't be that hard to manufacture, what size do you want?
I think we've discussed this before and I remember my concern being related to whether the levels of elements would be affected in the saturated salt water. I did monitor the measurable levels in the aquarium which had this system and for the most part they remained stable. The tank didn't have any dosing or supplemental systems so the levels weren't always perfect but did remain within reasonable tolerances. Basically I didn't notice any difference in stability before and after the system was installed.

[donlite]

This is a little of base but I am looking at having 2- 20 gallon plastic containers one with fresh water and one with high concentration of salt. When water evaporation is detected it acts as a auto top off system filling it with fresh water. When it needs a small water change using 2 salinity meters one in the tank and one detecting the water being mixed it can perform water changes. The system is not that simple but at the same time there is parts that you can purchase from robotic sites that are cheap and easy to hook up to your lap top. Let me know if this already exists and what you think, Don:idea:

[sphelps]

This is a little of base but I am looking at having 2- 20 gallon plastic containers one with fresh water and one with high concentration of salt. When water evaporation is detected it acts as a auto top off system filling it with fresh water. When it needs a small water change using 2 salinity meters one in the tank and one detecting the water being mixed it can perform water changes. The system is not that simple but at the same time there is parts that you can purchase from robotic sites that are cheap and easy to hook up to your lap top. Let me know if this already exists and what you think, Don:idea:
You don't need two salinity measurements, only one in the tank is all that is needed.

[Kybol]

what about something like this? I used one before and though maybe something along these lines would work?http://www.grasshoppercontrol.com/model62..html

You obviously wouldnt need the engine or blower. The hopper is all plastic, with a electric plastic auger running along the botton, with a gate valve type thing to control the rate into the fan.

Cant find a better pic though, sorry

[Bloodasp]

I saw this one yesterday. Don't know how good it is but might be worth a look. http://www.genesisreefsystems.com/categories.php?cat=7

[golf nut]

This was the original thread on RC when I asked the question.

http://www.reefcentral.com/forums/showthread.php?t=1623983

I really have no idea how a bucket of salt is produced, but if it all has to be mixed to get all the additives then I can see that being a problem, if one ordered a particular color of paint which came in paint ball size pellets and had to be mixed totally I can see that if a single pellet of black wasn't mixed with the rest of the tub and small portions were mixed frequently then one of the batches of paint is going to be very different.

If however the components in the bucket are a multiple of tiny amounts mixing short batches shouldn't be a problem.

This begs the question, is it OK to split a pail of salt with your friend?

[asylumdown]

You don't need two salinity measurements, only one in the tank is all that is needed.

I hope I've followed your original description of this system properly, but it sounds like you will first pump in a bunch of fresh water to the sump, and then gradually return the water to the correct salinity using the super saturated solution. Is that right?

would that kill stuff living on live rock you have in the sump?

[wolf_bluejay]

The original idea about this came from a sampling system for ocean water at different depth -- so pardon me if the idea sounds half baked.


Why bother with a hopper or motor controlled device that can cause problems -- why not have multiple "drops" of measured salt.

In the most simple but costly version: have 5-10 pvc tubes sealed on top with a flapper on the bottom controlled by a small motor each. Into each one goes to correct amount of salt for the mixing tank and all are placed above the tank. For a batch of salt, add water, open 1 tube, mix and serve.

On the cheap you could do a circle of tubes with flappers and a disk on the bottom with 1 hole in it. rotate disk a little and 1 tube opens through the hole.

A little less automatic for a whole bucket of salt, but would work well for 5,10,20 batches that you could measure out all at once and forget it.

[sphelps]

I hope I've followed your original description of this system properly, but it sounds like you will first pump in a bunch of fresh water to the sump, and then gradually return the water to the correct salinity using the super saturated solution. Is that right?

would that kill stuff living on live rock you have in the sump?
Pretty much, when water is removed from the sump the controller will continuously switch between fresh water and saturated salt water top offs to control salinity with the aquarium until the sump water level is restored. The top off flow rates are typically pretty low compared to the sump turnover rate so there should never be any large spikes of high or low salinity to affect anything in the sump or display. There's really no difference between this and a regular top off. A regular fresh water top off adds fresh water directly to the sump and it doesn't effect anything. Adding the saturated salt water will be the same.

You should however have the two water inputs upstream in the sump from the salinity probe otherwise the reaction time for adjustment may be too slow and you'll end up with a bigger range in salinity.

[sphelps]

Also so if anyone else is interested in another alternative to auto water change without a salinity probe you could setup something like this:


Two separate top offs will be needed, one for fresh and one for salt.
The fresh water top off is simply just your standard fresh water top off, set the float switch to trigger at your desired sump level. The only difference is you want the fresh water to be added slowly so use a small pump or restricted pressure/gravity feed.
The saltwater top off will require a decent size storage tank where you can store premixed saltwater (the same salinity as the display). Install a separate float for the saltwater top off slightly lower than the fresh water float. Just low enough so the saltwater float isn’t triggered from evaporation.
The saltwater top off should have a fast flow rate so use a decent sized pump.
Next install another decent sized pump in the sump to remove water quickly for water changes. You can use a timer to activate it or just a switch if you prefer to keep more manual control over the system.


That’s pretty much it. The fresh water top off will replace evaporated water, the slower flow rate will keep up evaporation since this is a slow process. When the pump in the sump is activated to remove water it will do so quickly and activate the lower float switch which will trigger the salt top off. Since the fresh water flow rate is slow the fast saltwater flow rate will top off removed water before much fresh water is added. To make up for the small amount of extra fresh water added during a water change to can keep your salinity a little higher in your make up container. How much higher will depend on your setup and may require a little experimenting.

To limit the size of the container you need for saltwater storage you can try using saturated salt water. You will have to experiment but by placing the saltwater float lower in the sump you can control how much saturated solution is added in comparison to fresh water. You will however have to maintain a constant salinity in the make up container. You can either maintain a high salinity by measuring or you can maintain maximum saturation by keeping temperature consistent and always making sure some salt remains undissolved

[golf nut]

You will however have to maintain a constant salinity in the make up container. You can either maintain a high salinity by measuring or you can maintain maximum saturation by keeping temperature consistent and always making sure some salt remains undissolved

Curious as to why you leave some undissolved?

I agree that supersaturation is the solution to an economical top off design but a number of questions have been raised and it would be interesting to understand how many of the questions are valid, usually we mix batches of salt well ahead of when we do changes, some say this is needed to allow all chemicals to mix thoroughly,can we take a cup of salt, mix and serve immediately with no adverse effects?


Liquid handling isn't rocket science, I use proportionalizer valves every day and they work fine, precipitation is another issue in premixes as I am told, which could lead to other problems, removing a known amount daily and replacing the same volume appears to be less constructive as doing larger batches fewer times... true false?

speaking of liquid handling.......http://www.wimp.com/beerscup/

[mike31154]

Automation can be a good thing, but for mixing your salt water? Come on, such a simple task and we try to complicate it by coming up with some ingenious, but quite technical and work intensive/costly ideas. How long does it take to measure some salt, toss it into your mixing container and give it a stir or start up a powerhead? Augers, valves, proportionizers..... egad. The maintenance of all the extra gear sounds like more work to me than just doing it manually. Apologies if I sound a little negative here, not really my intent, just trying to present the simpler point of view.

[intarsiabox]

I just use the highly advanced method of drawing a line inside a bucket, filling the water to the line and writing on the outside of the bucket how much salt is required to bring that volume of water to the desired salinity. Works every time and takes about 30 seconds a week to make up my water change water. No extra cost or maintenance. Nothing at all wrong with mechanizing things but its up to the individual to determine if it is really saving any time or effort.

[golf nut]

Automation can be a good thing, but for mixing your salt water? Come on, such a simple task and we try to complicate it by coming up with some ingenious, but quite technical and work intensive/costly ideas. How long does it take to measure some salt, toss it into your mixing container and give it a stir or start up a powerhead? Augers, valves, proportionizers..... egad. The maintenance of all the extra gear sounds like more work to me than just doing it manually. Apologies if I sound a little negative here, not really my intent, just trying to present the simpler point of view.

Do you have a rotary phone?

[intarsiabox]

Do you have a rotary phone?

Seen one for sale lately?

[sphelps]

Curious as to why you leave some undissolved?

I agree that supersaturation is the solution to an economical top off design but a number of questions have been raised and it would be interesting to understand how many of the questions are valid, usually we mix batches of salt well ahead of when we do changes, some say this is needed to allow all chemicals to mix thoroughly,can we take a cup of salt, mix and serve immediately with no adverse effects?


Liquid handling isn't rocket science, I use proportionalizer valves every day and they work fine, precipitation is another issue in premixes as I am told, which could lead to other problems, removing a known amount daily and replacing the same volume appears to be less constructive as doing larger batches fewer times... true false?

speaking of liquid handling.......http://www.wimp.com/beerscup/
Ensuring some salt always remains undissolved insures the salt solution is at max saturation and with constant temperature you can be sure the the salinity of the make up is consistent (max saturation at given temp). You could also in theory measure the salinity and keep it constant however it can be difficult to measure salinity of saturated saltwater and it's easier to just simply look for undissolved salt. It makes other options easier to employ as well. This is of course only important without the use of controllers, a controller eliminates the need to maintain constant salinity in make up water.

Some salts seem to require longer mixing times but I've used many salts that mix clear almost immediately and I've added cups of salt directly to sumps many times while preforming water changes without any adverse effects. Other peoples results may vary but I've never really pre-mixed saltwater ahead more than a few hours or so, typically I mix new water at the same time as I'm removing old water.

In the automated systems I've used and setup in the past I've always put importance on the less more often approach for stability. The systems would usually change a smaller percentage daily rather than a larger amount weekly or even monthly. This could very well be an important part of the systems I've previously described.

[sphelps]

Automation can be a good thing, but for mixing your salt water? Come on, such a simple task and we try to complicate it by coming up with some ingenious, but quite technical and work intensive/costly ideas. How long does it take to measure some salt, toss it into your mixing container and give it a stir or start up a powerhead? Augers, valves, proportionizers..... egad. The maintenance of all the extra gear sounds like more work to me than just doing it manually. Apologies if I sound a little negative here, not really my intent, just trying to present the simpler point of view.
Takes even less effort to top off your tank with fresh water compared to changing actual saltwater but most would agree a standard ATO is a must have these days. Not only to make your life easier but to promote stability. AWC is a very simple concept with a programmable controller with salinity measurement and employing a such a system is just another way to promote stability and free your time for more important things like actually enjoying your tank. If you enjoy manually mixing and changing water that's cool but most would agree it can sometimes be a hassle and often gets neglected.

[donlite]

What I have set at this point is very simple. I have 2- 30 Gallon drums (coke sells used drums for about $20). One is filled with fresh water and is connected to a float switch in my sump. The other tank has saltwater in it. I use one water lifting pump for the top off and 2 pumps for the water change. The water change pumps turn on and off together throughout the day. The problem is that the 2 pumps must have the same flow rate. I checked them and they are almost the same. I also have a second float switch that turns all the pumps off if something stays on or off. It is not a perfect system but it seems to work.:idea:

[sphelps]

What I have set at this point is very simple. I have 2- 30 Gallon drums (coke sells used drums for about $20). One is filled with fresh water and is connected to a float switch in my sump. The other tank has saltwater in it. I use one water lifting pump for the top off and 2 pumps for the water change. The water change pumps turn on and off together throughout the day. The problem is that the 2 pumps must have the same flow rate. I checked them and they are almost the same. I also have a second float switch that turns all the pumps off if something stays on or off. It is not a perfect system but it seems to work.:idea:
Yeap a very common method and works well for many people. With almost any system you'll still need to check salinity and make adjustments. Even systems with conductivity probes I still found the calibration/set points required slight adjustment every few weeks.

Rather than matching two pumps I find the use of float switches to remove and replace a consistent amount of water takes a lot of the guess work out.

[golf nut]

Rather than matching two pumps I find the use of float switches to remove and replace a consistent amount of water takes a lot of the guess work out.


Would a double stage cylinder be a better choice if it could be produced inexpensively?what volume would you need to move?

[wolf_bluejay]

Ensuring some salt always remains undissolved insures the salt solution is at max saturation and with constant temperature you can be sure the the salinity of the make up is consistent (max saturation at given temp). You could also in theory measure the salinity and keep it constant however it can be difficult to measure salinity of saturated saltwater and it's easier to just simply look for undissolved salt. It makes other options easier to employ as well. This is of course only important without the use of controllers, a controller eliminates the need to maintain constant salinity in make up water.


The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.

[golf nut]

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.



So how would you make a good solution that could be handled ?

[golf nut]

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.

This is a real question, I respect your expertise, what would be a better method?

[wolf_bluejay]

This is a real question, I respect your expertise, what would be a better method?

Sorry for the delay in responding -- been away a few days again :)

If you want to get really, really particular you could look up the solubility of each "ingredient" in the mix, and from the ration in the mix figure out how dense you could go.
Off the top of my head, I would be that it would be the calcium. as it is already super saturated in NSW anyways (magnesium is what allows this). As you start pushing the salinity to 2 or 3 times the normal amount, you could expect to see calcium precipitate out onto pump, glass, and everything in the super saturated hold tank. It will also push the equilibrium of the carbonate and probably cause issues with the buffering ("chalk" precipitate)

If you have a calcium reactor, or some cheap way of replacing the calcium you should be OK as most of the stuff in there does have a high solubility. Just always expect your salt mix to be very low in calcium and add as needed. If you are buying the super expensive salt with NSW levels of calcium, they you are wasting a lot of cash. IO salt is typically low on calcium and low in magnesium as well.

The best way, would be to not over saturate your salt as I'm not sure what else would go a little out of whack.

I'm almost thinking that the easiest and best way of doing this, is to just mix up a ridiculous amount of salt water at a time and do the "2 balanced pumps" to handle the water change -- mostly because I do add magnesium, some buffer, and calcium to get my cheap salt up to par and this might be easier with a larger volume of water. IE: 200 gal salt water storage in the basement and just change a few gal a day.
I don't think the salinity could get to out, and with a controller, you could just add some salt water instead of fresh to raise, or pump out a bit and add fresh to lower the salinity...... This way, you wouldn't really care what the salinity in the storage tank was (high or low) and let the controller work it out for you.

[sphelps]

The chemist in me really really cringed at this. Saturating the salt water mix is bad idea.
This would work IF we were only using one salt, but the mix is just that, a mix. All the different chemicals that make up our fairly expensive salt do not saturate at the same levels.
This saturation is used sometimes to purify (removed unwanted salts) in many production chemicals. The NaCl would be almost the highest solubility. So you end up with just mostly NaCl and almost all the calcium and trace minerals would be what would precipitate out of solution.


Think of it this way -- if you dumped a whole lot of salt mix and pushed it to saturation, separated the precipitate out, add more salt mix and repeat -- you would have some expensive NaCl without much else in it.
Yes this was my original concern with the method as well. However as mentioned I tested it long term on a reef tank with good success. I did not experience any precipitate and the levels in the display remained as consistent as the previous method of manually mixing and changing water.

When you think about it, it's no better or worse than how water is traditionally changed. Most people don't mix a full bucket of salt at once to insure optimal levels. Instead they grab a few scopes here and there which can result in different levels each time.

[sphelps]

Would a double stage cylinder be a better choice if it could be produced inexpensively?what volume would you need to move?
Not sure what you mean, can you explain? There is of course is a ton of different methods to remove and replace a consistent amount of water, I just mentioned one that I've used before.

[lastlight]

Yeah I'd love to be abler to mix up a full pail and then use 10g/week. Not sure having it mixing that long would have any ill-effects. It'd take me months to use it all right now.

I will use a pail a month with the new tank though. This might be the way to go. Params should always be consistent.

[golf nut]

Different manufactures have different method of producing salt, some will give you a pail of 200 white ping pong balls with 2 red ones 4 blue ones and 3 green ones, when all mixed you will have the correct proportions, but mixing in small batches could become problematic. I believe Tropic Marin has a method to give a perfect mix no mater how small a scoop you chose to mix.
I think Farley proved that doing daily changes was just as effective as mass changes, too much math involved for me to want to figure that one out.

Now all we have to figure out is the cheapest method of removing and exchanging a known quantity and put it on a timer to get the correct daily amount no matter what size tank you have.

[donlite]

In the end all I used was 2 aqua lift pumps and a 30 gallon tank from coke. The salinity is dead on. They turn on for a few minutes every hour and thats it. I have to use 2 pumps because if I drain first the 3rd aqua lift pump (for water top off, fresh water) will start up.It works very well but make sure the tubes do not fall out of the tank. I water top offed my floor for about 2 hours:redface:

[wolf_bluejay]

Different manufactures have different method of producing salt, some will give you a pail of 200 white ping pong balls with 2 red ones 4 blue ones and 3 green ones, when all mixed you will have the correct proportions, but mixing in small batches could become problematic. I believe Tropic Marin has a method to give a perfect mix no mater how small a scoop you chose to mix.
I think Farley proved that doing daily changes was just as effective as mass changes, too much math involved for me to want to figure that one out.

Now all we have to figure out is the cheapest method of removing and exchanging a known quantity and put it on a timer to get the correct daily amount no matter what size tank you have.

The more and more I think about it -- the more I'm convinced mixing large quantities at a time is better.

If you used a tall poly container 150-200 gal wouldn't take up much space, and I don't think you would need a large RO/DI reservoir anymore. Most people keep large amounts of RO water on hand for "emergencies", but having 200 gal of ready to go salt water I think would be even better.

As for testing -- I don't test my mixed water change water for anything other than specific gravity, as testing 25 gals at a time for alk, calcium, magnesium, etc would just be to much cost and a pain. But mixing 200 and testing it all at once would give a nice consistent result and would be easy to add calcium and buffer as needed.


As for the pumping -- I think that doing this with logic would be much easier than dealing with 2 pumps that you will never, ever get to be a perfect match without spending silly amounts of money.

For those than can follow controller logic:

1) pump in 2 gals, roughly
2) measure sality


repeat until just right (

if low -- do nothing and wait for some evaporation
if high add fresh slowly,

if just right -- pump out 2 gals, roughly

Basically, you remove some water and have 2 different "top-up" tanks, one salt and one fresh. Mix both to get things just right all the time, instead of having only a fresh water top-off.


If you get the mixing of the salt and fresh right on the controller, your change volume is controlled by how long you run the pump, and the system will "top-off" with the right mix of salt and fresh to re-fill the tank.

[lastlight]

So do you guys think it's ok to have a 200g reservoir of ready-to-go saltwater on hand? Let's say it gets fully used up in a month...

[sphelps]

I don't think it's reasonable to assume most can store 200 gallons of water, I've seen a 200 gallon poly tank and it's big and I can't see many people finding a convenient location for it. Some would even have trouble getting it inside.

Also 2 pumps could work and do work, most use dosing pumps which yes cost more than typical pumps but don't forget a controller with programmable logic and salinity control will run for at least $1000 so it's certainly not a cheaper option but I would agree it's a better one.

[Lance]

So do you guys think it's ok to have a 200g reservoir of ready-to-go saltwater on hand? Let's say it gets fully used up in a month...


IMHO, The saltwater should stay fine for quite a while providing it has some movement via PH and that it is stored in the proper container and cannot absorb anything harmful from the air of the room it is stored in.

[wolf_bluejay]

I don't think it's reasonable to assume most can store 200 gallons of water, I've seen a 200 gallon poly tank and it's big and I can't see many people finding a convenient location for it. Some would even have trouble getting it inside.

Also 2 pumps could work and do work, most use dosing pumps which yes cost more than typical pumps but don't forget a controller with programmable logic and salinity control will run for at least $1000 so it's certainly not a cheaper option but I would agree it's a better one.

Well, the cost of the controller I don't think could be rolled up into, as it has other uses as well. If oyu wanted to just go with some dedicated controller, I don't think the parts would cost more than about $50+ plus the sensor.

And if you went with the "salt and fresh top-off" the salinity of the salt water would no longer matter, as the controller would always work it out in the end. So if you did go with an increased salinity salt water (4x usual) you would only need 50 gal to store the equivalent of 200 gals of water change.
In my case I have a 220 gal tank, so I'm going on the high side of things with that in mind. If you have a 75 gal tank, you could put in a 20 gal salt water tank and hold the equivalent of 80 gals of water change.
Looking at a lot of fancy water change setups using brutte garbage cans, they have 50 gals of RO/DI and 50 gals of salt water ready. having 1.025 salt water handy would eliminate the need to store 50-100 gals or RO/DI water and have a much smaller fresh water tank.

Heck, with the controller taking care of things, you could probably get away with mixing the salt water at something like 1.015 or so, and most of the top-up can come from just the one tank assuming a few gal a day water change. Top up with 1.015 water, pump a bit out, and let evaporation do it's thing.

If you didn't have the controller -- you could (in theory) mix 1.015 water, have a small pump on a timer to remove a gal a few times a day, and have the 1.015 go in as top up. if you could find the right balance, between how much to pump out, and the density to mix up to match your evaporation -- it would work with constant tweaking. I just wouldn't want to have to watch things that closely.

[lastlight]

I don't think it's reasonable to assume most can store 200 gallons of water, I've seen a 200 gallon poly tank and it's big and I can't see many people finding a convenient location for it. Some would even have trouble getting it inside.

Yeah it's not practical for most but I'm designing a fishroom and may create a spot for one.

[sphelps]

Are you talking about building a controller for $50? I'm not sure about other controllers but to upgrade a pre-existing profilux to measure salinity you're looking at close to $400 with the sensor, the sensor alone is around $250. A two pump dosing unit to add onto a profilux is around $250 so this would be a cheaper alternative and realistically do the job just as well. I'll admit the salinity measurement is really nice to have as the options for changing and maintaining salinity are endless but I've used these units before and they require a fair bit of attention. I had to adjust the gravity offset every few weeks and often change the set points for the salt control.

If I where to go with a saturated method I would choose the salinity controller but if I was going to go through the trouble of maintaining a large amount of saltwater pre-mixed to match the tank then I would opt for the simplicity of two dosing pumps. Unless the tank was fairly large as dosing pumps would take too long to change a decent amount of water.

[abcha0s]

I'm going with the ~200 gallon storage container. I'm looking at the LiterMeter III peristaltic dosing pumps for the Continuous Water Change. The pumps are calibrated by volume, rather than time so minor differences in pressure can be accomodated. The ATO runs independantly and has nothing to do with the water change system. It's an incredibly simple system.

However, the purpose of my post was to share my experience with salinity probes. They are increadibly sensative to stray voltages and tend to wander all over the place. Curt at Apex recommends that the salinity probe be placed in a drip cup to completely issolate it from the sytem. I was never able to get a consistant reading from my probe and basically threw it out.

Another concern is the mixing rate of new saltwater coming in with tank water. I use this concept to monitor the pH of my system when topping up with Kalk saturated water. I have the controller set to shutoff the Kalk ATO when the pH hits 8.4 - However, by the time the pH sensor reads 8.4 the pH in my tank is past 8.5 - There is a delay in the reading but it's also partly how the kalk saturated water mixes into the tank and where the probe is located.

IMHO - I wouldn't trust a sensor to control/maintain the salinity in my tank. I think that you will be constantly adjusting minor fluctations in salinity either up or down. If your not careful, you may get a bouncing effect.

I also woudn't trust a cheap dosing pump. Thus, I'm prepared to spend the money for a high quality balanced pump setup.

[wolf_bluejay]

Are you talking about building a controller for $50? I'm not sure about other controllers but to upgrade a pre-existing profilux to measure salinity you're looking at close to $400 with the sensor, the sensor alone is around $250. A two pump dosing unit to add onto a profilux is around $250 so this would be a cheaper alternative and realistically do the job just as well. I'll admit the salinity measurement is really nice to have as the options for changing and maintaining salinity are endless but I've used these units before and they require a fair bit of attention. I had to adjust the gravity offset every few weeks and often change the set points for the salt control.

If I where to go with a saturated method I would choose the salinity controller but if I was going to go through the trouble of maintaining a large amount of saltwater pre-mixed to match the tank then I would opt for the simplicity of two dosing pumps. Unless the tank was fairly large as dosing pumps would take too long to change a decent amount of water.


The cost I was referring to was to build a simple controller for the salinity only -- not a whole controller -- and the $50 for the parts was an over-estimation. As for the cost of the salinity probe, the hardware is really only worth about $50-$100 for the probe. It would be even cheaper if you didn't bother with the "automatic temperature compensation" and assumed that your tank would not vary from 0-100 degrees.

Most of the profilux and other controllers are really, really pricey for what the hardware inside costs. Similar boards that support sensors, probes, relay outputs, and all the fun stuff are usually under $200 for the whole works. The extra cost is for making it pretty, including programming software, and customer support.

As for the peristaltic pump -- I just don't think they are quite up to the task of moving 50 gal a week of water. These pump are built to part time, and moving small amounts of water accurately. replacing a $250 pump about once a year adds up quickly.


I think that most of this was relating to the larger tanks, and larger equipment rooms/areas as I don't think I would go through the hassle of auto water changes on a 30 gal tank. I assumed that most people looking at this were in the same boat as me -- where doing 20-30 gal water changes a week just doesn't work with a bucket. If I could do my whole water change using 2 old salt buckets, I would go that way. But when you need 30-40 gal tubs just to mix the water -- 200 gal of water storage isn't too crazy when you have a 200+ gal tank and all the other gear that goes with it.

[golf nut]

I'm getting intrigued.

If I poured a gallon of ro/di water into a bucket containing 4 gallons of salt crystals then I anticipate that the solution would saturate then become stable, if I removed a known amount of that solution with a double acting cylinder and mixed it with ro/di in the correct proportions I should have a proper mix to be able to inject into the aquarium, if I then replace the saturated solution that I removed with more ro/di and at the same time remove the total mixed solution from the display tank and then repeated the process I should have a fairly accurate way of doing a water change , correct?

[sphelps]

Correct, so when will the prototype be ready?

[wolf_bluejay]

However, the purpose of my post was to share my experience with salinity probes. They are increadibly sensative to stray voltages and tend to wander all over the place. Curt at Apex recommends that the salinity probe be placed in a drip cup to completely issolate it from the sytem. I was never able to get a consistant reading from my probe and basically threw it out.


IMHO - I wouldn't trust a sensor to control/maintain the salinity in my tank. I think that you will be constantly adjusting minor fluctations in salinity either up or down. If your not careful, you may get a bouncing effect.

I also woudn't trust a cheap dosing pump. Thus, I'm prepared to spend the money for a high quality balanced pump setup.



Grumble, grumble -- Ok, I have to admit, you are right on this -- a lot of the idea of using the controller really depends on getting a probe that accurately measures things. The delay in measurements is not a big deal as you could just have delays put into the pump cycle -- pump for a minute or 2 -- wait 10 -- check ph, repeat.

But I could see most of these probes being affected by stray voltage, calibration drift, and general crappiness that would cause the system to mess up the tank parameters big time.



Has anyone done the math on how much the salinity would be affected over time by not using "matched" pumps? If oyu have 200 gal tank, doing 2 gal a day water change, and the pumps are out by a bit --- how much would things get out of whack over the whole ~200 gal water change?

[sphelps]

You don't need to match pumps if you use a float, I posted an explanation earlier involving a slow fresh water top off and a fast saltwater top off. Using such a method will result in stable levels.

As for conductivity probes they do fluctuate in my experience as well but with the right controller you get use to quickly adjusting the calibration/set points on a weekly bases to maintain consistent salinity.

[golf nut]

Correct, so when will the prototype be ready?
I am installing a swamp sump, hopefully soon.

When you mixed a saturated solution with excess salt always visible was the SG very constant? roughly what percentage of RO/DI did you add to get you to required levels?

[sphelps]

I am installing a swamp sump, hopefully soon.

When you mixed a saturated solution with excess salt always visible was the SG very constant? roughly what percentage of RO/DI did you add to get you to required levels?
If temperature remains the same then the saturation level remains constant meaning a constant SG as well, should be about 1.200 at room temp.

Saturated saltwater has a density of approximately 1.2g/ml at 21 degrees which is around 265ppt. Lets say you have 1L of saturated solution and your target is 35ppt. This means you'll need about 6.5L of fresh water to be added. So for every 1L of saturated salt, add 6.5L of fresh water.

[golf nut]

I think its time to do some testing with a 4 head peristaltic pump.