Ok I have a 55g planted tank that has been running for around 2years and about 8months ago one of my payara(scomb) got what i think was ick. So i went to the LFS and they sold me some maracyn2 which i put directly in the tank with the fish instead of setting up a hospital tank. Before this antibiotic the tank was fully cycled and running very well with allmost no ammonia or nitrite and the nitrate got up to around 20ppm every week the day of a water change. Now it has been 8months or so since the meds and i still do not have any nitrite and my nitrate doesnot go above 5ppm which is the same as my tap. But the ammonia gets out of control and i have been changing 50% every 3-5 days just to keep it under a lethal amount. So what is going on here? Do i need to totally tear the tank down and clean everything and start over from fresh. I wish i would have done this the first time the ammonia spiked and i would have a cycled tank again. please help ----------thanks