Thats all I use and not melted any yet so I guess either PH is staying where it should or ...........
tinytoon Reviewed by tinytoon on . Can rockwool melt!? and no, not by fire :) Acidity. The hydro shop owner said if I have a PH of 5.5 or below, my 4-inch rockwell cubes will start melting and shrinking...constricting my plants...therefore...killing them. Any truth? Rating: 5