Backyard Aquaponics
A place to discuss aquaponics

I have a feeling that if you would tranfer the fish to anew environment and alter the salinity at once that could expose the fish to ohter stress factor,
How long have the fish been in the tank? it could be New tank syndrome if you still have a reading for NO2 and NH3/NH4
At the temperature you have mention and with algae degrading, decaing feed stuck between the rocks and building up in the tank, BOD will defenetly be high and oxigen stravation is a possibility.
What source do you use for water top up?

The fish have been in the system for 4 months now without any unusual behavior or fatalities. I have been feeding them sparsely and always make sure all the food is eaten. What does BOD stand for? I have never seen the fish gasping for air at the top of the tanks as I have double venturi valve working around the clock for aeration. I have a 50 gallon barrel that I treat down in Ph with muriatic acid and use that water to top up. Due to my climate and the constant water temperature, I have a lot of water loss in the system due to evaporation, so it surprised me to hear that there might be a concentration of toxins building up, as I regularly add fresh water to the system. Thank you for your reply.


I have noticed that in my swirl filter bucket, there used to be much more algal growth resulting in long strands of algae. Now, there is definitely still algae, but it doesn't produce long strands anymore and seems to be less active in the swirl filter.

Not sure but might he mean Biologic Oxygen Demand? That would seem to fit with what he is saying. With decay happening and algae not healthy, you might be fighting a losing battle with DO.

The build up of any potential toxin will definitely happen if it is in your water and NOT off-gassing or evaporating. If it is coming in with the water you are not diluting it you are increasing the amount each time.

Is there a Uni close where you might be able to get the water tested for contaminants? I'd take 2 samples, one from the source and one from your FT - the difference between the 2 might be easier to spot.

More experienced AP'ers might have a different explanation but from what I have read gasping fish are being deprived of enough DO. Maybe get an air supply other than the venturi and put it in - if the fish then congregate around the bubble stream you could have your answer.

If the water has been sitting around for a day or so in the hospital tank it should be close to the same temp as the normal tanks. I'd put the fish in then slowly bring the salt in, let them adjust for a while to the new salt level then add some more etc. I wouldn't add the fish to an already slated environment, given they are possibly stressed already. Take a few hours to bring the levels up.

Regretfully another fish went his way today before I could get them into the hospital tank. All done with the move now. Nice clean fresh water and the remaining fish look happy and well oxygenated. They are fast little buggers and it took longer than expected to move them.

I'm thinking a combination of factors are contributing to the fish loss, but mostly contamination from what I gather. Next on the list is a hose down of the tanks and water change. I will bring the salt concentration up slowly and leave them in the hospital tank for more than a week most likely.


As for which kind of salt to use, I've heard many things and it's still not clear. The two I've heard the most are pool salt and sea salt. Any final recommendations from the crowd?

Thanks again.

Not iodised. Run a Search using this - salt +tank - the plus says it needs to find tank as well as salt in the post, so you're more likely to get results dealing with salting FT's instead of what to put in the recipe. Pool salt seems the most common recommendation

I seem to recall advice not to use table salt at all because it has something in it... (anti-ckaing ingredietn?) In Australia you can check ingredients on the side of packs - not sure if that's the case in the US.

I've done some research in UK pond salt industry and it turned out that even some type of pond salt contains anticacking agents too, so I would question your source if you can.
A word of advice when selecting salt is to buy natural sea salt (health store, internet)
Most salts are made of sodium chloride, what do you want in your system is the the Chloride, that is the component that keep down NO2(like a steriliser) and increase mucous slime coat production on fish to help keep healthy, Sodium in AP will not be so much of any benefit.

Here we have something called Maldon Sea Salt, maybe there is a similar source of good quality sea salt there too.

The specific brand of salt recommended to Australian members... is a pure sea salt.... as are the vast majority of pool salts...

Isnt all salt composed primarily of sodium chloride (NaCl) regardless of where it comes from??

Yes and no..... what we commonly refer to as "salt".... whether sea salt or table salt.... is Sodium Chloride....

But in a chemical "salts" definition... it could be something like Potassium Chloride.... which is actually a good substitute if available... as it provides the beneficial "chloride" as noted... but also provides a more beneficial input for plants... Potassium.. as opposed to Sodium...

Theres just so much to know with so few brain cells left

I wonder if this would be a good salt to use.
I read items mentioned and as a novice have no idea what would be better use. I am having fish problems and now I have to salt in the system and a high ph. 8.4

The HTH 8-pound Salt Restore and Balance protects against scaling. It also controls metal staining. The Non-Chlorine Oxidizer will remove bather waste, suntan lotion while reactivating chlorine. Maintains crystal clear water and helps maintain the pH level. Treats 20,000 Gallons. Active Ingredient-Potassium Peroxymonsulfate 32.3-34.3-percent.

I wouldn't use it, it sounds like it has lots of additives. Stick with pure pool, solar, or sea salt.

OK so I found some Morton solar salt in crystals, active ingrediant sodium chloride could not see any other ingredients on the packaging. Took it home, disolved it in unclorinated water. I have over a 180 gallons of water and used about 20 cups of salt to slowly bring the salinity up. I then added to FT a little while later foam or what looked like washing bubbles. I guess its telling me to start over, clean my FT as current occupants have opted out and start over. sucks for my GB,I keep airation going in case I missed a fish or two who might still be alive, but stopped cycling to the GB. This solar salt crystals must have more than the packaging states or my system is pretty messed up. Tonight I will drain the FT clean it well with vinager water and start over and make sure the water is set, PH \ Salinity \ before adding occupants.

Newb from Illinois.

I would agree that removing the rocks in the fish tank altogether would be a good idea. I had to learn this lesson the hard way, but that could be the problem.