I am having trouble with water becoming infected with ammonia. I do part water changes daily. The tanks are 30 gal bare bottom. Fillters were sponge and box but I have since changed to internal canisters. I feed discus frozen worm , discus meal, twice a day. May be I am over feeding them?
Over-feeding is a bad practice or habit of feeding.
Feed the amount they can eat within 5 minutes.
Feed them little bit at a time.
Allow them to have time picking up uneaten food.
Any type of filters will be good as long as you do not overfeed them.
Once the uneaten food get into the filter system, it will circulate the ammonia instead.