The type of stone in it can boost hardness. People use coral (well washed/soaked), oyster and other shells, etc. You can buy powdered shell and egg shell combos, or make your own. Do a little research and find something that you want to use...
I try to do the "natural" approach first and chemicals as a last resort. You need to decide how you'll approach it. There are several options out there.
Well since I don't have any coral around me at all and I can't really go to the LFS right now, I'll go the simple way, with the GH booster
A friend of mine agreed to give me some until I can order my own.