I don't waste time with 20-30% water changes---do 90%+ Twice!
DON"T reduce the ammonia---ELIMINATE it!
Water bad enough to stress tilapia with ammonia is caustic enough to actually dissolve the spine margins of the dorsal and tail fins of tilapia.
Here is what the fluidized bed sand filters I use allow me to do...2000 5 inch tilapia in a single 150 gallon aquarium---12 fish died in 10 days.
