I just use Stress Coat. If I remember right Amquel is to get rid of ammonia in the water if your water tests to have too high of an ammonia level. If it's Amquel Plus, it would do that plus remove chlorine. Novaqua is like Stresscoat I believe, dechlorinates, helps add the protective slime coat etc. Both of my tanks are cycled so I don't have to worry about high ammonia levels.