I would assume that the aqueous solution would be the best. However, I would
purchase it from an aquarium store as I think the aquarium product is a
weaker formulation and would be safer for the fish. I don't have any at the
moment to check the concentration or usage rate and I would be careful of
commercial grade material in case it is a lot stronger???
Adrian.
Adrian R. Tappin
Brisbane, Australia.
"Home of the Rainbowfish"
http://www.ecn.net.au/~atappin/home.htm