I have a 20 gallon tank that is planted with a banana plant, some amazon swords, some valisneris (probably misspelled that) and some java moss. For some reason, there are extremely high levels of ammonia in the tank, and I can't figure out what is causing it. I have done several water changes, which drops the ammonia levels, but over night they spike back up again. I've had to remove all my fish from this tank due to the ammonia. Any thoughts on what could be causing the ammonia?