Backyard Aquaponics
A place to discuss aquaponics

I have a bunch of Blue Tilapia fingerlings. Started with 20, now im down to 16 after a week. I was checking every day for floaters, but wasn't seeing any, so I thought all was well. But last night I found 3 dead ones on the bottom in various places. Today I found another one. There don't seem to be signs of ick or any other sicknesses, but they are still dead. I thought maybe the fact that they didn't float at all may give a clue as to what happened but I haven't found anything about that anywhere as a symptom. Oxygen shouldn't be an issue, as I'm using a pump that can handle a tank twice this size. PH is about 7.6+ (7.6 is the max my testing kit can read and it's never read any lower than that, even on my tap water.), but they should be hardy enough to handle that right? I doubt ammonia would be the problem, as it is at .25ppm. Water temp is about 15 Celcius, but again, I believe they're hardy enough to take that and shouldn't need a heater unless i'm gonna breed them. All of the remaining fish in the system seem as happy as can be. Plenty of activity, no signs of disease or discomfort that I can tell. I'm just puzzled as to what could have caused these four to die off. Any suggestions as to something I may need to fix would be greatly appreciated. The fish cost me more than I would like to admit and I don't want to loose any more of them.

I would be checking your pH with another kit that can read higher than 7.6.

Also what is your nitrIte reading?

I'd suspect water temp to be honest.

Sounds like pH issue, but I'm a newbie.

I suggest you buy another pH-test kit that uses a wide spectrum.
I bought this test online last year for about 10€. Guess you can get it in Canada more easily then I could in Sweden...


The bottle says "500 test" but that's with a full vial and two drops. If you just fill the vial half way and use one drop you get 1000 readings.

Being in Australia I've had nothing to do with Tilapia, but I've done a fair bit of reading on them and must say I agree with Bodgy... it's temperature. From what I've read 15C is the lower limit of their temp range, but 18C+ is recommended... and if they are young fingerlings they will be much less likely to withstand extended periods at their lower temp limit... just my opinion.


P.S... I did read one article recently that suggested Blue Tilapia in particular could handle temps down as low as 8C, that article stuck in my mind because every other article I've read recommended much higher temps... If true, I would imagine 8C would only be for very short periods.

P.P.S... When you say your water temp is about 15C, how are you measuring it and at what time of day?... could it be getting colder than that in the early morning hours?

Thanks for all your responses guys, I'm off to get a heater and another PH test kit. Found another dead fish this morning *facepalm*. By the way, it is an indoor system, so I don't think temperature swings will even be a factor, the temperature remains constant at 18-19 (Kind of hard to read the cheap thermometer I have). And yes, the Blue Tilapia are supposed to be the most cold hardy type, so I was expecting room-temperature-ish water to be ok for them.

15 is a low, but I had some mossie tilapia make a entire winter outside and the water temp was way below 15C. Blue should be able to handle that temp, but they might not eat. I went through a spell when I was loosing lots of tilapia and my water temp was fine. All parameters where fine, still not sure what killed them, but they died one at a time. I have not changed anything in a while and my fish seem to be doing fine.

But to make a winter in Canada you are going to need some serious heat. 15F for weeks at a time is no big deal, but for long term they won't make it.

Ran a wide spectrum PH test on it this time and PH seems to be hovering around 8.0. Got a heater as well but I'm still not sure I'll need it. As for the PH, I went ahead and made up a peat ball out of an old tube sock. That should be able to bring the PH down slowly, which I hope will solve my problem. Due to the high PH, it sort of goes without saying that my plants are almost completely wiped out. I just have the one yellow bean plant (growing veeeery slowly), a few seedlings I can't identify, and an apple tree which I am no longer certain if it is alive or dead, lol. I have other plants but I'm not going to even try transplanting them til I get this water sussed out.

Still loosing fish here, I'm down to a dozen now, I think. I've tried adding 1ppt iodized sea salt in case of parasites or something. Added plants in case nitrate toxicity was the issue. Reduced their feed amount in case it was overfeeding. Even dosed them with this Ick Attack stuff in case I'm somehow blind and am not seeing any of their symptoms. Temp is now holding at ~20C, PH still at ~8, almost no nitrites, ~0.25ppm ammonia, nitrates ~150+ppm. The latest deadie looks all chewed up like the others were eating the body. I watched them all for a few minutes. They are energetic and, well fish-like, for lack of a better term. There is the fact that some of them seem pale, in that their top colors seem faded, which kind of puzzles me, cause I can't find that anywhere as a symptom of anything. I'm at a near-complete loss of what the problem is and what to do at this point? Do I just ride it out and hope the remaining ones just get over whatever's wrong with them?

Temp.

When we talk of max/min. temps, let us not forget that this is for adult healthy fish.

We are talking fingerlings here, you wouldnt expect your 6 month old baby to survive extreme conditions that you just could, would you?

So, what temp are we talkin here, like 30C? The water seems pretty warm to me as it is.

It will, you are in canada where it snows.
Tilapia if i am not mistaken are from africa where it never gets close to snowing.
You see where i am going with this?

i would say a minimum of 22 or so should be ok, shouldnt be too much for the power bills and will be warm enough for them to survive, but 25-26 would be better i imagine.

Can you post some pictures?

I'm no expert, following this thread with great interest though.
The nitrates seems very high, and you don't have that many plants left you say?

Perhaps planting some fast growing plants temporally might help. Like wheat grass or mustard or mustard.

do a water change, i didnt see the 150ppm, that is definitely too high.

can you give us details on your system too?

big ph swings can kill your fish, but high ph shouldn't, unless the source for the fish was low, and you shocked them when you stocked your system..did you slowly acclimate them?
don't used iodized salt.. there may be anti-caking agents that are not good for fish
if you only have access to a grocery store, use "kosher" salt, and salt to 3ppt... i use "pure" water softener salt when needed, a 50lb bag was cheap
and yeah, 15c is too low for tilapia, the ones that do survive will grow very slowly