most use hydroton,but where I live there are no hydro shops so Im forced to have to mail order all my supplys.the cost of shipping was almost as much as the hydroton so I had to find a cheaper way,what I use is very small pea gravel,actually its for fish tanks I had it from 1 of my large tanks that I had to shut down to move,its natural stone not the colored stuff,Im on my second grow with it and it works fine,I guess you could add a little pearlite to it if you wanted but I dont, hope this helps and good luck