There seem to be a million choices on different web pages, and ebay has tons of them, some being really cheap. What do you look for in a ro/di unit and any reccomendations?
I see big price differences in different ones, but I have no knowledge as to what makes them worth their price, or what I should use in reef keeping. I've just been using ro/di drinking water, and I have no clue what process that goes through.