No you do not have to use RO water. Depending on the quality of your tap water you may want to fill your tank initially with tap to get started then later when doing partial water changes you could use RO water. RO water has virtually no minerals so you would need to add a reconstituting agent if you use pure RO in the beginning. I have found that plants grow better in softer and more neutral to acidic water. Much tap water is hard with slight tendency to the basic side. Some plants such as Val may grow OK in harder water but most seem to better in softer/acidic water. Hope this helps. Eric --- StripMime Report -- processed MIME parts --- multipart/alternative text/plain (text body -- kept) text/html --- ------------------ To unsubscribe from this list, please send mail to majordomo@thekrib.com with "Unsubscribe aga-member" in the body of the message. Archives of this list can be found at http://lists.thekrib.com/aga-member/