You said these are Tilapia? I would lower to about 75 degrees, slooowwlllly. I can't calculate your dose, as I don't know how many gallons of water you have. I have you should see change in behavior after about 30 minutes of having added more air. It doesn't take long to see improvement. Maybe not a total fix, but at least an improvement. When I am having a really hard time, I put a 20 inch box fan blowing acrossed the top of the tank. Not sure if this does anything but the logic I use, is that I am changing the air out over the surface, allowing fresher air to come in contact with surface. The more surface area you have the better the gas exchange. Not sure if perceived or real, but I think this helps some too.