The black one with holes sounds like your black carbon.
Not sure what the stones are.
Post in tropical discussion, more members go over there.
Sounds like your in the uk if you are using anti fungus and finrot med by interpet.
What are you treating for?
How many gallon or litries is the tank.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.
What's the name of the filter.