Flow Rate Closed/Open Systems

[HaZRaTTy]

Hey,

Again I'm struck between the flow in my 70G Reef. I have been trying to research and figure out whats best but there is so many arguments bordering both sides that I would apprecaite a few peoples opinions and suggestions.

I haven't bought a return pump from my sump yet so I'm open to ideas. Here are a few things that are clear like MUD

Flow through Sump? - GPH on Return Pump? Head of Approx 3 Feet? Suggestions on a model of pump.

Powerheads? Should I be aiming for about 25x Water Cycle? Which would put me at approx 1700GPH?

The water cycle through your system isn't measured by the water flowing through your sump but more the Amount of Flow in your tank?

So If I aimed at around a 500-600GPH Return Pump and made up teh 1000GPH in Powerheads would that be sufficient in Flow for LPS/SPS?

Appreciate any clearing of the mud anyone can do.

[Myka]

The magic number through the sump for a reef tank is 6x turnover per hour which allows the entire water volume to be processed approximately 99% in 24 hours. Anything much more than that will only achieve washing of microbubbles to the display tank (not pretty, can irritate corals). 6x through the sump will provide the protein skimmer with the right amount of new water to be as efficient as possible. The skimmer can only process so much water, so washing a bunch of water through the sump real fast doesn't help the skimmer, and just wastes electricity. Some people argue faster flow when they use filter socks, and say the filter socks process more water with higher flow. My argument against that is if the socks can't keep the tank clear with 6x turnover then the tank is probably overfed, overstocked, or has poor circulation within the display tank.

For SPS I like around 60x turnover just with powerheads, for LPS 30x turnover is good. Some SPS tanks will have over 100x turnover...I have never tried that much. For a mix tank, 40-60x turnover is good...have areas of high flow and areas of low flow and sort the corals accordingly. Try to have lower flow near the sand (use smaller powerheads lower in the tank) where the LPS will be, but make sure you have enough down there that detritus isn't settling on the sand.

For a pump, add the display tank volume with the volume of water in the sump. Say about 85 gallons total. Multiply that by 6 is 510 gallons per hour. So pick a brand, and pick a model that is close to 500-550 gph at the head height of your tank (measurement from the pump to the highest portion of plumbing in the return line). For this size tank Eheim are great pumps, and they just put out a Compact series which are cheaper. I don't mind Quiet One pumps, but they aren't as quiet as their name suggests. Mag Drive pumps are loud, and I would not recommend them. Poseidon are external pumps and are very good, dead silent pumps, but are becoming harder to find.

[kien]

Hey,

Again I'm struck between the flow in my 70G Reef. I have been trying to research and figure out whats best but there is so many arguments bordering both sides that I would apprecaite a few peoples opinions and suggestions.

What's best for your tank is one part trial and error and one part personal preference. Some guys like to blast their tanks with so much flow that they can not keep a sand bed down. Some hobbyists are at the other end of the spectrum. In either approach you have to keep an eye on your corals sort of observe their health and behaviour. Some corals will like lots of flow some not so much. This is why opinions are all over the map on this subject. You can see in this thread where some people sit with flowrates in their tank.. http://www.canreef.com/vbulletin/showthread.php?t=48372&highlight=flow

I haven't bought a return pump from my sump yet so I'm open to ideas. Here are a few things that are clear like MUD

Flow through Sump? - GPH on Return Pump? Head of Approx 3 Feet? Suggestions on a model of pump.

The flow through your sump should be well matched to what flow rate your skimmer can handle. Every pump you research will will have an adjusted flow based on head loss/height.

Powerheads? Should I be aiming for about 25x Water Cycle? Which would put me at approx 1700GPH?

Again, one part personal preference and one part trial and error.

The water cycle through your system isn't measured by the water flowing through your sump but more the Amount of Flow in your tank?

I'm not sure what you mean by water cycle through your system. Do you mean the water that enters your display tank via the return pump and then out of your tank via the overflow? or do you mean the water that's being pushed around your tank by powerheads?

So If I aimed at around a 500-600GPH Return Pump and made up teh 1000GPH in Powerheads would that be sufficient in Flow for LPS/SPS?

Maybe yes, maybe no? Different corals appreciate different levels of flow. You have to observe them to see how they are behaving and reacting to the flow you're giving them. That may be enough for some corals but may not be enough for others. That may be too much flow for some corals.
You have to also consider the quality of your flow as well. It isn't as simple as counting the flow rate in your tank and calling it a day. Some people can get away with a very low flow rate in their tanks because the quality of their flow is quite good.

Appreciate any clearing of the mud anyone can do.

responses in magenta.

[HaZRaTTy]

Myka Thanks for the Reply.

So I'm looking at the Mag7

http://www.jlaquatics.com/product/wp-mag07/Danner+Mag-Drive+700+Supreme+Water+Pump.html

I will also be aiming at 2 - 1400Gph Koralia Powerheads and a smaller powerhead that's pointed to the bottom.

3 Powerheads that could look quite cluttered in a smaller reef I guess that's the price you pay.

[Myka]

I edited my post. I don't recommend Mag pumps for anything other than mixing salt. They are noisy and I have had trouble with them not restarting after power outs.

I have 4 powerheads and a Wavebox in my 90. :D

[kien]

I edited my post. I don't recommend Mag pumps for anything other than mixing salt. They are noisy and I have had trouble with them not restarting after power outs.

I have 4 powerheads and a Wavebox in my 90. :D

Perhaps the older ones were louder? I run a mag 12 and a mag 18 in the return chamber of my sump and I can't hear them and no one that has come over has made mention of their noise. Perhaps they are louder outside of the water? Prior to running the mag18 I ran a QuietOne3000 which was anything but quiet. Damn that thing was noisy, even muffled by the water I could still hear it.

[Myka]

Hmm, weird. I've always found the Mags to be much louder than the QOs - especially the bigger Mags like yours. My tank is almost silent...the only thing I can hear is the Tunze 6055 ramping up (it's on a controller) and the Wavebox pump kicking in. Not even a hum though, just barely a sound. Can't hear the skimmer, the overflow, or the return pump.

[HaZRaTTy]

Okay,

So I figure I will have approx 4-5'' of head pressure to deal with and sitting around the 400-550Gph through the Sump I have found the Lifegard Aquatics Quiet One 3000 Water Pump

It's 67$ from JL and I think will the the trick just fine.

[globaldesigns]

I edited my post. I don't recommend Mag pumps for anything other than mixing salt. They are noisy and I have had trouble with them not restarting after power outs.

I have 4 powerheads and a Wavebox in my 90. :D

Actually I differ... I used a Mag 18 pump for a couple years without issue, and they are not noisy at all. At least mine wasn't. They are rugged and work nicely, also they are very compact in size for the power they produce.

Now in saying that, as I recently went on holidays, and my pump is 2-3 years old, I replaced it and kept the old Mag as a backup (I didn't want to take any chances, with me not being around for 2 weeks). I wanted to try the Eheim (model 1262), so I did and can say it is also quite quiet.

If I was to compare the 2 brands I have now used. I can say the Eheim is quieter, but that is compared by putting my ear against the sump glass, outside of that, I can't hear either. Even though the Mag 18 is rated with more throughput overall, I do think the Eheim is rated lower, even though it isn't. My reasoning on this is that the water flow through the system is comparable between both models.

[ScubaSteve]

What are you planning to keep in your tank? I do almost all SPS and have a crazy flow through my tank... probably somewhere in the range of 35x to 40x, but that is very turbulent flow so the actual water velocity isn't high enough that it lifts my sand. Again this is preference and I have found this through experimentation. For softies and LPS I'd go much less than this but some of my LPS. like my Ducans, love the flow.

As for flow through the sump, there are few different views on it. I'll give you the chemical engineering point of view first. If you treat the sump as a place to put your skimmer and are designing it as such, it actually doesn't matter what the flow rate is through the sump. Imagine your skimmer hanging off the back of your tank with no sump; it will process XXX GPH of that volume and, at least for this discussion, the skimmer doesn't really care a whole lot about how the water is moving around it. Now imagine grabbing a small section of your tank and stretching it off to one side so that the total volume is the same but part of it is just moved to one side; this is your sump. Put the skimmer there and look at the system again. Again, the skimmer processes XXX GPH of that total volume and it doesn't matter a whole lot how the water is moving around it. The biggest determining factor of skimming ability is the amount of contact time between the water and bubbles inside the skimmer, not necessarily how the water is moving around the skimmer.

Yes, if you match the flow through the sump to the flow through the skimmer, you can kind of, in very loose terms, say that all the water entering the sump is going through the skimmer. This in theory should give you a concentrated waste stream entering the skimmer and a purified stream leaving the skimmer. In a situation where you want to have a separate product stream of the most pure water you could get, this is what you want to do... but after we clean it, it gets sent right back to your display to mix up with all the other dirty water. So what is the point in this approach? (other than saving energy that is) In fact, a skimmer's efficiency goes down as the inlet concentration of waste goes up.

Put very simply, the skimmer is just an exit point for waste products from on otherwise closed system. The flow patterns around it don't, for the most part, matter. So, if you have a sump flow rate that far exceeds the skimmer's flow rate it doesn't matter; you just end up "cleaning" less water on a per pass basis but your total water volume will still be turned over the same (which will depend on your skimmer size) regardless of flow rate. So why not use the sump as a blend between a filtering section and closed loop system? I'm actually building a new system around this idea as we speak.

Now, from a practicality point of view, Myka is right. If you have a super high turn over through the sump you just end up pushing bubbles into the return pump and into your display. Bubble removal depends on the time it takes for the bubbles to reach the surface... so for a given flow rate, the bigger sump, the more time the water has to "de-bubble" before going back to the display. If you can remove the bubbles faster, then you can run a smaller sump. You and I are going to be running the same return flow, the only difference being our sump size. Mine is a 15G (not by choice but by space limitations) but I want a high flow to remove at least 1 or 2 powerheads from the display. Because of this I've had to come up with some fancy ways of removing bubbles faster to avoid the bubble issue with the faster flow.

There is also the matter of debris: a sump is a great place to settle out debris. So, just like the bubbles, a lower turn over will allow more debris to settle out before being sent back to the display.

Soooo... ranting finished... design your sump based on what you want it to do and your space requirements. Design what is right for you. Don't design it around the skimmer's flow rate. If you want it to have a high flow through it to act as a sort of closed loop, you can do it! You just need to keep practicality in mind while implementing it. Build the biggest sump you can to get the best performance but don't be afraid to be a bit more aggressive with your designs.

Also, I use the Mag 9 for the same pressure head as you. I'd use the Mag 9 over the 7 and throttle it back with a valve if needs be. I have no complaints with the Mag pumps but recommend Ehiem's if you can afford one of the higher flow pumps. Ehiem's are so nice and quiet.