Backyard Aquaponics
A place to discuss aquaponics

Hello to all aquaponics enthusiasts. I am relatively new to this hobby. Built my system and started it this January. I have a 275 gallon fish tank (IBC) that gravity feeds 4 GB... 2 of which are constant flood and two flood and drain (IBCs cut to 14"deep) GB are filled with 1/2 " pea gravel. All GBs drain into 275 gall sump. From this sump, water is pumped back to FT. After cycling the system with goldfish, placed about 40 1" tilapia end of May. In two months, some fish reached 6", most were at 4.

System works well, and ammonia and nitrite levels are at 0... ph stays in 7 to 6.8 range and nitrates have gone up to 40 several times, but tend to stay around 20. I've been trying to experiment with different plants and as I pull a large batch off, NO3 would spike, but plants absorb it quickly, especially grape tomatoes.

Several days ago found fish floating, being eaten by others. Two days ago, found another one, slightly alive, but others were nibbling on it and scale was gone... I took it out and dissect it to see if maybe it ate something.... nothing looked suspicious, but there was a large sack filled with clear yellowish liquid... Today, came from work, another one is dead...

We had a lot of rain here in NE Florida, tested the water and it was acidic 6.2

I'll try to post some pics of dissected fish... not sure if its ok to do that here... please let me know if you have any ideas.

Thank you very much in advance.

What's your water temps been sitting at?

No white spots on the fish? Gills wide open? Bellies sunken in?

Water temperature has been around 83-85 F or 28 to 29C

No spots on fish, gills seems to have a normal pinkish color. .. not red

All three fish had no scale, but it might have been an effect, not the cause

I noticed that there are 2 or 3 larger fish that are territorial and a bit aggressive. ..




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I also run an air pump in the FT periodically. ...

used to run it all the time until several months ago air hose failed and somehow syphoned the water back to the box and killed the air pump...



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This is the picture of the inside. .. I think the clear sack with yellow liquid is actually the stomach. ..

never see clear stomach in a fish



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Tilapia are quite hardy. Only time I loose fish is if DO is low. I have had DO as low as about 2 if I remember right and no deaths. They weren't happy while skimming the surface for O2. Check DO. If you don't have a DO meter, then add a decent air pump anyway.

It seems that yellowish sack is just under the skin behind the front fins..

How could that be... I'm thinking physical damage.. Chiclids can be very aggressive.. but don't quote me..
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I think the yellow sack is actually the stomach. .. intestines coming from it is also clear and yellowish

Galaxy far far away