a friend treats his entire system at a shop with it and the tanks without extra airation has all the fish gasping at the surface a few hrs after treatmant.
i used it and had the same affect, added a couple of airstones and blasted in the air everything was fine.
have you noticed the foamy bubbles on the top after treatment? i think the treatment reduces oxygen exchange at the surface.
might be compleatly wrong and some know it all may jump in and say " you compleatly wrong sharp tooth" as whats getting to be quite normal on here.
BUT its not gunner hurt makeing sure there is plenty of airation in the tank.