Got a refractometer and WOW, way out...gotta fix

[Slick Fork]

Hi there,

Just got a new refractometer in the mail today and wow was my hydrometer ever out. My Hydrometer was telling me I was at 1.024 and the new refractometer says 1.030. 6 POINTS OUT!!! I expected to see a difference but that's huge.

So anyways, I wanted to bring my salinity back down to 1.024 and my plan is really simple. I don't want to do it all at once of course but I figure if I pull a couple of litres of SW out every day and top back up with fresh RO water that should be slow enough do you think? The system is a 100gal display with ~40 gallons in the sump.

Is my plan to aggresive, or to conservative? Should I maybe just do my adjusting during water changes? Let me know what you think.

Cheers

[Zylumn]

Same thing with me when I got my refractometer I was blown away at how many ppl my hydrometer was off. As I said before my hydrometer worked fine but they just glued the numbers in the wrong spots.

[wickedfrags]

Sounds like a reasonable plan. I would think 2-3 litres a day will do the job until you get it down to where you want it. Some people (inluding myself) maintain their salinity at 1.026 so you do not have to drop it down that much if you don't want to.

Hi there,

Just got a new refractometer in the mail today and wow was my hydrometer ever out. My Hydrometer was telling me I was at 1.024 and the new refractometer says 1.030. 6 POINTS OUT!!! I expected to see a difference but that's huge.

So anyways, I wanted to bring my salinity back down to 1.024 and my plan is really simple. I don't want to do it all at once of course but I figure if I pull a couple of litres of SW out every day and top back up with fresh RO water that should be slow enough do you think? The system is a 100gal display with ~40 gallons in the sump.

Is my plan to aggresive, or to conservative? Should I maybe just do my adjusting during water changes? Let me know what you think.

Cheers

[Reefer Rob]

Double check your refractometer with Pinpoint 53.0 uS calibrating fluid. Many of the refractometers that find their way into the aquarium trade are for testing brine not sea water, and will give you an inaccurate salinity reading

[Slick Fork]

I ordered it from J&L so I would hope that it's one meant for the aquarium trade! I did calibrate it with the "ultra pure" water that came with it. Is that alright or should I locate some of this pinpoint 53 stuff?

[Okguy]

I would confirm the refractometer readings first before making changes. Take a water sample to you're local store (if there is one around) and have them confirm the readings. If the livestock doesn't appear to be stressed with your current water parameters, you might as well take your time and make sure the changes are required.

I once made slight changes because a new thermometer I bought was faulty and the consequences were pretty severe. Just better to be safe than sorry.

[Slick Fork]

Unfortunately there's no LFS around that deal in SW stuff. Closest would be Calgary and that's a 2hr drive for me. Are there any other ways I could confirm the reading? Livestock isn't visibly stressed at all so I'm not in a panic, it'll just bug me now that I know about it!

[Reefer Rob]

Stability is more important than the actual level. A reading of 1.030 on the refractometers they sell at J & L is probably about right, as they read high. They also sell the 53 uS calibration fluid.

For more info read this thread (http://www.reefcentral.com/forums/showthread.php?s=&threadid=953605)

[ron101]

If the readings are accurate and you want to drop from 1.030 to 1.024 you will need to swap out about 25 gallons total (assuming total volume of 125gal) - more if you are doing it incrementally.

If you use RO water you will probably have to supplement more calcium and carbonate additives to keep overall levels up.

[midgetwaiter]

You can make your own calibration solution by following the info in this article:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

You really want to do it with a scale though and make sure you get the solution right. The AMI calibration solution is cheap enough that I wouldn't bother.

My refractometer was pretty good at first but it has been off more and more lately, probably dropped it or something. I was just lucky enough to have heard about the potential problems with the calibration already so I didn't go and screw anything up. If your livestock looks good make sure you can confirm your measurement before you change something.

*EDIT*

I don't like the coke bottle thing in the article and I had a few minutes to kill so I figured out how to make up a decent solution if you don't have a scale but do have a fairly precise liquid volume measure. You need to mix 3tsp table salt in 491ml RO water. Assuming that the tsp of salt measures 6.2g, it should be pretty close, that will give you a solution that should read 35 ppt or 1.265ish.

Turns out the calibration I did to my RHS10-ATC based on a Deep Six hydrometer reading was bang on. :) Back to the drawer with the refractometer.

[crystalz]

I also started with a hydrometer. Hydrometers shouldn't even be sold as a salt/sg measuring device. My refractometer was a real eye opener for me too. Hydrometer was way out.

[Slick Fork]

Thanks for all the help so far! So I did an improvised DIY solution following the basis of the reefkeeping article. I used 1927ml of RO water, and mixed in 1/4 cup (73grams) of Salt... The salt was easy to measure with a measuring cup and I used another glass measuring cup to get 1900 ml of water, I used a syringe to add the final 27 mL of water so I'm fairly certain I was precise.

I did this mixture 3 times just to be certain I didn't screw up somewhere :lol:

Now, just to be sure when he says "Morton's Iodized Salt" he's talking about an American Brand name for table salt correct???

This mixture gives me the 3.65% ratio of salt to water I need to adjust to a 35 ppt reading on the refractometer. I took 3 readings off each batch, every reading of every batch was within .005 of 1.029 so I proceeded to adjust my refractometer to 35ppt or 1.026.

So, with all that done do you guys think I could be confident trusting the reading I'll take after supper?

Thanks and Cheers

[Reefer Rob]

You should get the Pinpoint fluid before you change anything. No rush, corals can thrive in a pretty wide range of salinity... as long as it's stable. If your tank looks good, don't mess with it! Refractometers should sold with a 35 ppt calibration fluid.:rolleyes:

[midgetwaiter]

Thanks for all the help so far! So I did an improvised DIY solution following the basis of the reefkeeping article. I used 1927ml of RO water, and mixed in 1/4 cup (73grams) of Salt... The salt was easy to measure with a measuring cup and I used another glass measuring cup to get 1900 ml of water, I used a syringe to add the final 27 mL of water so I'm fairly certain I was precise.


Your math is right and the fact you got the same result 3 times is a good sign. It comes down to how precise your measures were, a good scale would work better than volume measurements.


Now, just to be sure when he says "Morton's Iodized Salt" he's talking about an American Brand name for table salt correct???


Yep.


So, with all that done do you guys think I could be confident trusting the reading I'll take after supper?


I think you should be fine. Please post the measurement you get with both devices now that you've calibrated, it sounds like they'll be pretty close.

[Slick Fork]

Ok, so using my DIY calibration fluid as described above, here are my new results.

The refractometer out of the box tested the 35ppt solution at 39ppt, it tested my tank at a salinity of 40ppt. After calibration with the DIY fluid my tank tested at ~36ppt (sg1.027). so that sounds ok, it was 4ppt high. Still higher than I would like but a lot less earth shattering than my original reading of 1.030.

I adjusted the solution as per the article for a hydrometer as well and found that it supports the newly calibrated readings from the refractometer. It gave me an adjusted reading of 1.0265 for the tank water

So it seems that the calibrated hydrometer supports the calibrated refractometer and I can be fairly confident that my refractometer is now accurately reading salinity right?

Sort of disappointing to find that a $65 piece of equipment billed as a must have for reefkeeping was less accurate out of the box than a $10 plastic instant ocean hydrometer.

[Reefer Rob]

LOL that's how I felt when I first found out. Try using one for 2 years and then you find out it's been inaccurate all that time, and your little swing arm hydrometer that everyone snubs was actually reading more accurately.

Still, once you get them calibrated correctly they are indispensable.

[Slick Fork]

So, this is interesting....


After deciding that the refractometer was off by using the home-made recipe discussed above, I decided NOT to make any changes until I could pick up a bottle of the pinpoint 53 ms solution and get a "third opinion". I'm glad I waited

When I calibrate the refractometer with the 53ms solution, I discovered that my home-made solution was off, and that my original calibration was correct! It now reads distilled water at 0ppt and the 53ms solution is 35ppt. So, I guess I can draw several conclusions

#1) It looks like I got a dead-on refractometer after all!

#2) It pays to check, double check and quite often triple check the calibration of stuff.

#3) I proved that I can make the wrong solution exactly the same 3 times in a row and all that it proved was none of my wife's kitchen measuring utensils are as accurate as they should be. My confidence in the next batch of gravy is going to be a little shakey :lol: :lol: