ok question . will be buying a ro/di unit. any idea what one to buy . witch one does most of you guys use and do you like it and where did you buy it from.
also i am topping my tank off currently with distilled water. is that ok ?
While it's possible to get a really questionable RODI unit off of e-bay, as long as you buy one from a reputable seller as Jason listed, you can't go wrong. A properly configured and maintained RODI is a pretty bullet-proof piece of equipment, and the brand has a lot less influence on quality than other pieces of reef equipment such as pumps and heaters.
Using distilled water to top-off is OK in the short-term, but make sure that you're getting
distilled water rather than "purified water". Purified water for drinking has had substances added back to it so that's palatable for drinking (principally calcium and magnesium salts). Also, realize that some "distilled" water is
actually distilled rather than being purified by RODI. That could be a problem, as copper evaporators/receivers are often used in these types of stills.
