I have a 33 gallon freshwater aquarium with 10 neon tetras and a Dwarf Gourami. My pH level currently reads 6.5-7.0 (JBL COMBI Test kit) On my last visit to the LFS, I came across some great looking rocks (PAGODA).The sales guy told me they wouldn't cause a problem with my set up. Said I should only rinse them and add to my tank. So I got 3 medium sized rocks. Now I'v just read that these rocks may change the water chemistry!!!! (pH, Fe, KH) How far is this true? If it IS true is there any way I could treat the rocks befor I add them?