Don't use growstones! They're loaded with lime, CaCO2, which ruins pH control. I've been battling pH swings from hell thanks to these rocks. Trust me, you don't want to be in the position I'm in right now. My plant looks horrible.
I've been researching around and have come to the conclusion that neoprene sponge foam cubes are the best medium ever. They're sterile and 100% inert out of the box. No washing or stabilizing needed. Only draw back is you have to buy a roll and cut out the cubes yourself. Once I finally give up on these grow stones, I'm going to give them a try. Amazon neoprene sponge foam too see what I'm talking about. They come in varied thickness.