Salt Mixing Anomaly

[Bradlas]

I don't even knpw where to begin. But this has dumbfounded me. I'm using Brightwell Neomarime and RODI which always mixes to about 7.4 dkh for me. Suddenly in the last two months, and despite switching to a new bucket of salt, I mix up a 5 gallon batch and the alkalinity is 5.8. After several attempts to change the way I mix I get the same result. Last night I decided to use soda ash to up the dkh to 7.8 (+2 dkh) in order to do a water change and I wake up this morning and the result was 4.8 dkh. I used a different hanna checker and a new reagent and the result was 4.9 dkh on that test. I am using a pump to keep water moving throughout. It does generate some heat in the water due to the pump I believe (it's also quite an old pump). Does anyone have any idea what coukd be happening or what I could be overlooking? I am totally stumped!

 

[mike550]

@Bradlas I started to get really wonky Alk readings from my Hanna. Turned out it was old reagent. That said if you’re using two Hanna testers and different reagents I’m inclined to think its your salt.

Did you mix up the container to help redistribute the salt mix? Maybe some settling occurred. Otherwise maybe a bad container?

 

[jda]

It is a good idea to keep a cheap Salifert Alk kit around just to double check your other things. It is worth

You could be precipitating carbonate and calcium out of the water. I have never used Brightwell salt, so no idea if this happens. It can happen with others.

Did you dry mix your salt? I know that BRS said that you don't have to, but they are completely wrong, IME. Unless you add the whole container/bag, I would always dry mix it.

 

[ScottB]

Double check your refractometer already?

 

[Bradlas]

I checked my refractometer using brightwells calibration fluid and also compared it to a mix of salt weighed out and measured with water of the correct proportion to get as close as I could with the refractometer. Today I decided to try again after doing this. This time I placed 5 gallons of RODI in a bucket, put 325g of Salt mix slowly and then 45 minutes later I added the other half of the salt. The salinity was spot on the refractometer. (I'm using a lowes bucket so I know it isn't quite 5 gal. Which is why I didn't use quite as much salt as brightwell says I need). I have now measured alkalinity again 1 hour after mixing in the other half of the salt and I am reading 6.1 this time. The salt is clear and looks good. I usually let it stand at least 12 - 24 hours before testing or a W.C. Should I keep the lid on or off? Should I aerate? Could this be an issue with RODI? It shows 0 TDS.

 

[Randy Holmes-Farley]

I checked my refractometer using brightwells calibration fluid and also compared it to a mix of salt weighed out and measured with water of the correct proportion to get as close as I could with the refractometer. Today I decided to try again after doing this. This time I placed 5 gallons of RODI in a bucket, put 325g of Salt mix slowly and then 45 minutes later I added the other half of the salt. The salinity was spot on the refractometer. (I'm using a lowes bucket so I know it isn't quite 5 gal. Which is why I didn't use quite as much salt as brightwell says I need). I have now measured alkalinity again 1 hour after mixing in the other half of the salt and I am reading 6.1 this time. The salt is clear and looks good. I usually let it stand at least 12 - 24 hours before testing or a W.C. Should I keep the lid on or off? Should I aerate? Could this be an issue with RODI? It shows 0 TDS.

The only explanations that come to mind are test error, or a bad batch of salt mix. Allowing it to sit or aerate is not going to increase alk.