ok so i read an article about what 2 feed ottos and they said a piece of zuchinni so i put one in the tank. it also said to leave it in there no more than 3 days b/c ottos like when it gets softer. when i woke up in the morning, the next day, the water smelled aweful and was filthy as heck. i took the zuchinni out and did about a 40% water change. it didnt change anything. will this go away with water changes? is it harmful to my fish?(neon tetras and black phantoms and ottos)