I'd use your tap water if you possibly can. RO water is a lot more work. If you can raise babies in your water, they'll be much better acclimated to it. If you can get the parents to spawn in such hard water, that is. I use Seachem Equliberum (for GH), Alkaline Buffer, and Acid Buffer(for ph, KH) to adjust my RO water to the proper GH/KH/pH. My well water (pH 9.2 before RO) AFTER the RO treatment has a pH of 8.4 but it quickly drops (1 - 2 days) to 7.2 pH because there is no KH to keep it stable I suppose. It will not go lower than that. That being said, I must wait two days before I use my RO water. I have 3 32 gal. Rubbermaid food grade containers. I transfer the RO water from the newest made container (8.4 pH) to the other containers where I can usually count on the pH being 7.2. But because there is practically no GH or KH, I must use the Seachem products to adjust depending on which fish I'm using it for. What a pain. If anyone has a better way, I'm up for suggestions.