Dan -
I know most of the above comments are addressing your additives, but I would also like to comment on the inhabitants of your tank. IMHO a 29G tank is much too small for a Hippo tang (12.2" when they are full grown). An engineer goby will also quickly outgrow your tank. Other inhabitants seem fine. Since you only have one Percula, maybe you could get another one of those. They may fight at first (depending on their age), but I think that would be a much better choice. If you have your heart set on having a goby, maybe one of the Shrimp Goby (there are quite a few that do not exceed 5" full grown).
Anybody else want to comment on this issue?

BTW - Welcome to MAAST


Wendy