yea it does, I didnt know how it would work, but nothing happened, didnt seem any stress in the tank or anything, So I was happy with it..It does not contain phosphate, does contain aloe vera which they say helps reduce stress or healing. I also read some things from other users, which were good but suggested not to use it in a planted aquarium because it stunts algae growth, which turns plants yellow and then they die. Which I did not have.