Backyard Aquaponics
A place to discuss aquaponics

So I have a mix of catfish, jade perch and silver perch in an IBC system with around 900L of water. THeres a heater in the water that keeps it between 22 and 24 degrees C, and the entire tank and GB are in a greenhouse.

Last week i removed a yabbitat that I had built in there, as I hadnt seen any live yabbies crawling around for some time. This stirred up a lot of silt, and the water became quite murky, so i let things settle, and the water started to clear over the weekend. Yesterday, I came home and there were 2 fish, (1 jade, 1 silver) floading dead, though they did look like they had been dead for a while. Today, another 3 (1 jade, 2 silver) floating. They also looked like they might have been a couple of days gone.

Tested water 0 ammonia, nitrates and nitrites,Carbonate hardness (KH) around 180ppm, general hardness 30, PH of 6,6

Any suggestions for further tests, ways forward etc, much appreciated.

I can't think of anything right off to suggest. Do you have a system thread with pictures? It sounds like your fish tank is accumulating too many solids.

Could that silt been anaerobic and toxic to the fish?

System description and photos would help.

No current photos, as its always dark by the time i get home. Its a basic IBC with a flood and drain cycle completing every 8 mimutes. The pump is solids handling, and theres 2 airstones in the water too. Also recently added a pressure filter.

Heres my original post with my system viewtopic.php?f=18&t=20029 - the main difference being that its now inside a cheapish greenhouse, mainly to protect it from the wind, as too many plants were dying in the strong winds in my backyard.

There could have been loads of nasties in the silt that clouded the water when i removed the yabitat. There was certainly some evil smelling residue in the yabitat when it came out, but the tank water has no odour to it, and is now relatively clear.

D

ok I remember your build now, sorry I can't help with the fish problem.

is there anything else which may have affected them?

Feed, additives, whatever? odd you have 0 am, NO2 & NO3

I will retest again tonight.

The newest addition is the pressure filter. It also has bioballs, so that could account for the low amm, NO2 and NO3.

I am hoping it is all explainable by the sludge lifted when i removed the yabbitat, and that now its all settled, there wont be any further die off. But with no definitive explanation, i am still quite concerned.

I added some salt to the water last night, as it had been a long time since i had, but ive misplaced my refractometer.

I think Slowboat is on the money
"Could that silt been anaerobic and toxic to the fish?"




(There could have been loads of nasties in the silt that clouded the water when i removed the yabitat. There was certainly some evil smelling residue in the yabitat when it came out, but the tank water has no odour to it, and is now relatively clear.[quote="Slowboat"]Could that silt been anaerobic and toxic to the fish?)

(I am hoping it is all explainable by the sludge lifted when i removed the yabbitat, and that now its all settled, there wont be any further die off.)


I base my assumption on your your descriptions above, without photos it's hard too tell what the problem is but I would agree with Slowboat, there's always going too be problems with that sort of muck on the bottom of the tank, it can't be of any benefit to the system at all. The fact that it's now settled doesn't help the water quality, water quality and over feeding are two of the main killers of fish in tanks.

No change in water test results today, but more importantly, no more dead fish!

Perhaps they were just sleeping. Or maybe there was a power struggle for turf in the tank, were any of the dead fish wearing colored bandanas? The Yabbitat may have been a stash house for one side and you accidently started a gang war by it's removal.

Sorry couldn't resist hope your die off is over. Isn't there a way to avoid sludge build up in the bottom of the tanks? If thats fish poo shouldn't that be being pumped through to your grow beds? I'm just new to the aquaponics but I havn't heard of anyone using algea eaters and snails and I wonder why not.

Any answer to this would be great.

Cant answer about the algae eaters, i thought about some muscles, but dont know enough about best keeping them. Snails can tend to get eaten by the fish too.

Anyway, 3 days, no fish deaths.

Water murked up again, could be the food.
In separate news, found a rather large gravity filter on sale for $170 so bought it. Now to figure out how to get it high enough.

Have you used any product to clear your water??

One more dead fish today.

Water still testing fine. Cleared up a lot.

Now added a gravity filter (which is harder than you might expect on a above ground IBC system)

I am also going to get new food for the fish, as every time i feed them, the water seems to cloud a bit.

Did the silt on the bottom release bubbles when you moved it?

Not that I saw, but its not impossible.