Backyard Aquaponics
A place to discuss aquaponics

Hi all,

I have a small 55 gallon system with 34 tilapia and a few goldfish in it. The system has been running for several months with the goldfish and about a month since I added the tilapia. They have all been doing great! Until a few days ago when I finally got around to buying tilapia food. Before, I had fed them small pellets for omnivorous fish from the pet store. But I ordered a bunch of tilapia fingerling pellets (they are all fingerlings) and started feeding it to them. Suddenly my smaller tilapia started dying. I have now lost 14 tilapia (goldfish are still doing well), mostly the smaller sized ones, and some of the others don't look too hot. I also had my Ph drop to 6.0 for some reason.

My question: is it possible that the new feed could have something to do with the deaths? I wouldn't think so, but it seems pretty suspicious that I've had a really healthy system running and the only thing I changed was the food.

Any advice would be appreciated- thanks!

What is your water temp? Ammonia? Nitrite?

Ammonia, nitrites and nitrates are all at zero. Water temp goes between 75-80.

It's unlikely that the food caused the deaths, probably just a coincidence of timing. Does the feed smell like it's gone bad and is this feed larger or smaller than what you were using?

The food smells pretty normal, and I just ordered it through Premium Fish Food, so its probably fine.

The food is larger than they are used to, which did worry me a bit. But it's been less than a week since the new food, and I also included the old food when feeding them so they can have a slow transition.

But I think now I just sealed the fate of the remaining fish...I added a small amount (or what I though was a small amount!) of calcium hydroxide to try to raise the ph a bit, and it just tested at over 7.0...pretty big jump in a day. Poor fish.

we have had a new food kill a heap of fish on our farm, they were trialling higher levels of phosphorous in the food and turned out whatever they used killed fish. Only killed trout, salmon were unaffected. they now use a different chemical to get the phosphorous into the feed.

Could be the food, you will never know unless you trial on 2 different tanks, one with normal food and one with new food.

34 tilapia in 55 gallons? Water quality aside that seems a little energetic.

How's your aeration? With those warm water temps, is it possible that the new food went uneaten and caused a bloom that could have reduced O2 below critical?