The proper way to use it is in a fluidized reactor, it's far less efficient in a bag and has a greater chance of turning to a solid mass. If you have never used it before, I would suggest using 1/4 of the recommended amount for your size tank to start with and move up from there. PhosBan works fairly fast and can cause problems if not checked. I think the manufacturers recommend one gm per gallon, but I would start out with much less and test frequently in the beginning.