Bigger filters do not mean more bacteria I'm afraid. They just mean more water flow. The bacteria will live anywhere there is a biofilm - in the filter and on every surface in the tank.
Was the ammonia under control but it's just gone up or has it always been above zero? If it's just gone up, have you done anything that would have killed some bacteria, or added more fish?
Was the ammonia under control but it's just gone up or has it always been above zero? If it's just gone up, have you done anything that would have killed some bacteria, or added more fish?