Has anyone ever heard of using charcoal rocks instead of gravel in a freshwater aquarium?

Question

I picked up a used aquarium and it included what I was told was gravel, when I bleached and boiled the rocks though it turns out it wasn't gravel at all but charcoal, is this done for some special reason in a freshwater tank or were they making a mistake with it's use? I've always used regular gravel myself and have never heard of using anything else.

Yes I realize charcoal is used in filters but they had two inches of charcoal in the bottom using it like gravel!!

Answer 1

I have never heard of that being done on purpose before. If I were you I would toss it and replace it with regular aquarium gravel. If they did that, no telling what chemicals might be in that charcoal.

MM

Answer 2

Charcoal is a very good filter medium. It is used in many domestic filters.

It is also used in aquarium filters so, either the gravel contains a certain amount of filter material or some got spilled from the filter.