Anything that removes ammonia is bad for your tank. It will prevent your tank from cycling if it isn't already and if your tank is cycled you shouldn't have any ammonia anyway. If you are cycling with fish and have an ammonia problem, I suggest you try to lower it with frequent (as many as 2 or 3 a day if needed), small water changes or as a last resort, using a product like Ammo-Lock that changes ammonia to a non-toxic form. I don't like the chemicals since you still get an ammonia reading and it is supposed to be non-toxic, but for me there would always be that worry as or whether it really was or not.