Some say to dissolve it in a glass of tank water but i never do I just pour it in the tank in a area that get alot of flow. It will dissolve on its own. Maracyn and maracyn2 can be bought at most lfs's and around here its at meijer's. if you can not find maracyn than use another antibiotic. It is more important to get the fish treated before death occurs. Even if it is not the 100% correct antibiotic for the job.