Aquarium charcoals are all pretty much the same. Alternatively, you could buy a bag of natural "lump" charcoal for bbq's at some stores, this is the kind that is just burned hardwood chips, not the briquttes. Lump charcoal has no chemicals or fillers in it like the briquettes. Wal-Mart carries it, though at this time of year they may no longer stock it. Making lump charcoal is a simple process, you burn clean hardwood chips in a clean enclosed vessel that has a vent to control the oxygen level the way a charcoal grill does. The wood needs to just char thoroughly, not burn away to ash.