Refractometer, what to believe.

[Docdiggy]

I had many things die and I'm convinced my salinity was high and the cause. I bought the aquamaxx seawater refractometer to get to the bottom of this. The directions say you can use RODI or calibration fluid. With RODI my tank shows about .027 and the pinpoint calibration fluid puts my tank at about .023-.024. I really don't know which to believe. All my sps were dying and a local shop owner who uses RODI to calibrate showed my water at .030 while my BRS fluid showed .025. I got rid of all my sps and kept the lps. I have since lowered my salinity and am seeing improvement. I just don't know what to believe.

 

[Scotty Buttons]

Do you mean 1.023 1.024 1.027 1.030?

 

[Docdiggy]

Yes

 

[Fishfinder]

Those could all be accurate results depending on your tank setup. How big? ATO? But salinity from 1.023-1.027 won't kill SPS

 

[Docdiggy]

It's now reading 1.027. Before I was getting a reading as high as 1.030. I also lost 2 fish. It's about a 100 gallon system that I top off daily.

 

[chipmunkofdoom2]

You should trust the calibration solution.

While refractometers designed specifically to measure seawater should accurately calibrate with freshwater, there are a number of reasons why this might not be the case. Calibrating with freshwater will only produce accurate results if the refractometer was specifically designed to measure seawater and does not have any other problems. Calibrating with a salinity standard will always ensure that you read accurately at S=35 ppt.

I expect if you calibrated all of the refractometers used with the same salinity standard, you would get the same result when reading the same sample.

 

[Docdiggy]

I hear ya. I could not find any other reason for things dying except our difference in salinity readings. My new refractometer says it's made for seawater.

 

[Randy Holmes-Farley Verified Community Expert]

None of those values will kill SPS corals. I’d look for a different explanation.

 

[Docdiggy]

1.030 for months?

 

[Randy Holmes-Farley Verified Community Expert]

1.030 for months?

I doubt it. Only the shop showed it to be high, and that is probably wrong, but even so, its not especially likely to kill corals at that level.
sg = 1.030 is 39.8 ppt. The average salinity of the Red Sea, where corals and fish thrive, is about 40 ppt.

 

[Fishfinder]

Also topping off daily can give you those fluctuations depending on tank size and evaporation. But I don't think salinity caused your deaths, especially your fish

 

[Docdiggy]

Well I was wondering if the fish deaths were because of all my sps dying. Maybe ammonia from them. An API test showed 0, but that's API. I just matched pinpoint from marine depot and the other one I got from BRS and they matched the same.

 

[Docdiggy]

I think I'm gonna send water out. Any comments on Triton vs ATI?

 

[James Johnson]

If you are using API test kits that's probly half your problem, I would get some Red Sea or salifert test kits and re-test everything, also there is a lot to be said about tank maturity especially if you are new to the hobby. I usually wait till the tank is about 6 months old before adding sps or difficult to keep corals.

 

[NY_Caveman]

I have that refractometer. It seems to work fine, but I will note, I calibrate it every time I use it with RO/DI. I am guessing the screw adjustment is touchy because it is a tiny bit off each time I pull it out.

 

[Docdiggy]

I only used api for ammonia. I use red sea, salifert, and Hanna testers. This tank has been up for about 5 yrs.

There is a pretty large difference if I use RODI vs a calibration fluid. I bought the BRS and pinpoint fluids and they test identical. However, calibrating with fluid shows my tank at 1.023 and RODI shows my tank at 1.027-.028.

 

[PhreeByrd]

I also suspect that salinity had nothing to do with your issues.
For future reference, use specific gravity only if you're measuring with a hydrometer, and note that this is a pretty reliable but roundabout way of measuring salinity. A refractometer measures density (still in a roundabout way), and the concentration units (i.e., 35 ppt) are more direct and useful. Choose one and stick to it. Overall, the focus should be to keep salinity constant rather than to keep it at specific (and often pretty arbitrary) level. Even if your readings are not perfectly accurate, test with the same method and keep the salinity at the same level according to your test method.

 

[Sleepydoc]

I have that refractometer. It seems to work fine, but I will note, I calibrate it every time I use it with RO/DI. I am guessing the screw adjustment is touchy because it is a tiny bit off each time I pull it out.

Mine is often off slightly (or more) - there doesn't seem to be much rhyme or reason as to when or by how much it's off. I've gotten into the habit of calibrating it each time I use it. Theoretically, you can calibrate a refractometer anywhere on its curve, so RODI should work, but you are always best off calibrating at or close to the measurements you are taking so using a 35 ppt/1.026 calibration fluid is best.

I agree with the other posters that the readings you're getting don't explain the coral or fish deaths.

For Ammonia test kits, either Salifert or Red Sea works well - I find Red Sea easer to read but it takes longer.

 

[Perkins]

Mine is often off slightly (or more) - there doesn't seem to be much rhyme or reason as to when or by how much it's off. I've gotten into the habit of calibrating it each time I use it. Theoretically, you can calibrate a refractometer anywhere on its curve, so RODI should work, but you are always best off calibrating at or close to the measurements you are taking so using a 35 ppt/1.026 calibration fluid is best.

I agree with the other posters that the readings you're getting don't explain the coral or fish deaths.

For Ammonia test kits, either Salifert or Red Sea works well - I find Red Sea easer to read but it takes longer.

I have a Red Sea refractometer and it seems the the temperature change causes it to be off it is usually pretty close as long as the temp in my house is steady but if I get a big change in temp it’ll be off more than just a slight change in temp I use my rodi water to calibrate every time I use it. I also use the same light in my house every time

 

[tiomm]

I had the same problem. Some corals would not acclimate and died, while some new additions would be grumpy for a few days and then do fine.
I noticed that I needed to use 420 grams of salt to every 10 liters of RODI to make 1.025 water using Red Sea blue bucket. According to their specs it should be 382 grams.
My refractometer was calibrated with a calibration fluid that I trusted.
But then I recalibrated using 20 degrees Celsius RODI and the refractometer was way off. After that I tried mixing 382 grams of salt and it said 1.025. Now I have brought the salinity down and my corals look way better after just one week. Conclusion; never blindly trust your calibration fluid.