Hi, I have a 18 month old hexagon aquarium with tropical fish. I treated it with Lifeguard over a month ago due to fin rot. Since that time, my cycle has crashed. The ammonia readings are off the charts high. Even doing a 50% water change still results in an ammonia reading of 1-2. I’ve lost fish due to this and am really trying to do what I can to put a stop to it. I have vacuumed the gravel often to clean up waste. I’ve cut back on feedings. I tested my tap water and it has zero ammonia. What do I do? I don’t want anyone else to die, but even doing huge water changes isn’t helping.