I am in the process of learning about a planted tank, I need help! I have decided to go from a predominantly fish oriented aquarium to a more balanced environment, with plants and a few fish. Which water is the easiest, cheapest and over all most practical for water changes? I have a "Tap Water Purifier". My favorite store sell and promotes R/O water. This seems the best, I have full control over the chemical state. R/O water can be expensive, they want .50 cent a gallon. I can get Distilled water for about half the price. The distilled water seems to be the same pure composition as the R/O. Is this correct? If so, water is only about ten bucks a week, minus all the fertilizer, trace elements and hardening agents. Or am I going in the wrong direction? Any other advice would be appreciated, I've read a few books and now I only know enough to kill a lot of plants and fish!