Tilapia bloated stomachs

[Gary Wong]

I've got an IBC system, about 200 FT, and 100 GB.  The Tilapia started to die about 4 mos into having the fish in there. I stopped feeding, but they would get a bloated stomach and then die 1-2 days later.  This has been happening for 2 weeks now, no feeding and still get 1-2 fish with bloated stomachs that will probably be dead tomorrow.  Clearly I'm not overfeeding at this point, not sure why they have such extended stomachs and what the treatment is.

[Keith Rowan]

have you dissected any of them?

[Gary Wong]

Thanks Randall.  You mentioned over use of salt but Epson salt might help? I'm wondering if some perlite got into my fish tank and causing this problem.  At any rate, fish are dying and doesn't appear I can do much (tried partial water changes, stop feeding fish, feeding small amounts of duckweed lately to give fiber).  

[Kent Evans]

Gary,

Where did you get the duck weed?

Just a thought.

[Gary Wong]

Duckweed is grown at home for over a year.  I did a partial water change and put my UV filter in there (from my aquarium).  No fish death since then, although the guy in the photo I think is a gonner sooner or later.  Was overcast today, they swim at the top during the day when it's hot.  This system is above ground and with no shade.  I wonder if the water is getting too hot reducing the oxygenation.  I have an air bubbler and there is a pretty strong water fall from GB to FT (sits on top of it).   Still yet, do you think that's too much heat?  Hope not cause it's mid 80's during day now, and in summer will have days of mid 90's on occasion.