I have a HOB filter, and i just put the bag in the filter, after the charcoal..
if my memory serves me right they make a powder.. i have only had experience with the bags... ( i could have been thinking about something else though..) anyway, just put it in the filter and it will do the job..
Which reminds me.. i should probably get a new one? lol..
also, this may sound silly, but a new bulb may be the trick.. that bulb you have may have sat around for a long time before you bought it, or may have been used, or a number of things.. I know that the flouresant actinics actually have a shelf life.. possible that MH does also.. i know they both contain gasses.. like i said, i cleaned my lights, and the glass and the green stuff is going away... many different things could be wrong, best to start eliminating them one thing at a time.. :joy: