Substrate for acf

[theomega]

What substrate should I use for an AC F. I tried sand but it ended up turning black and had a bad smell like rotten eggs I would like to use large pebbles but I'm afraid the pellets would get stuck. Do you think a glass bottom would work?

 

[elKendo97]

Perfectly, the bare ground is the most practical.

 

[Asevernnnn]

That shouldn't happen to sand normally, did you have more than an inch of sand in depth?