Backyard Aquaponics
A place to discuss aquaponics

I have something weird ( I think) going on with the salt level in my tank. I have Silver Perch in my 1000 lt tank and for a while I had a reading of salt at. I had put some salt in last year. I then started changing some of the water to lower the salt. It was suggested i get it down to between 3 - 5 ppt.
Now what happens is I get the salt down to 2 - 3 and then in a couple of days...it is back up to 4 - 5. I am using town water or rain water to top the water up. Both have salt of 0.

I think I read that Barra produce salt? So my question is, are my SP's producing salt? Several times I have gotten the salt down to 2 and then in two days. it is back to 4 - 5.

Any ideas?

Thanks,

Linda

Hi Linda

my first question would be what are you using to measure your salinity and are you calibrating it before each test?

I am using a refractomitor. And not sure what you mean by calibrating it. I am washing it off each time with tap water, which is 0 salinity, and checking that it is reading 0 with that.

The fish would need to "add" 1 kg of salt... in your 1000L tank... to raise the salinity by 1ppt...

Not possible...

My refractometer needs to be re-calibrated before each use using distilled water as the test liquid Igregory, this may not be the case with yours but usually a fine measurement tool such as a refractometer needs a recalibration at some stage. Have you got a pic or some details on the brand you are using?

Indeed.. is it an ATC... auto temperature correcting... model... if not it will read widely inaccurate with differing temperatures...

can you get accurate measurements using a hydrometer, comparing specific gravity to a sample with a known salt concentration?