Hi, I have had a saltwater tank for almost a year now and am looking into getting an RO/DI unit. It is rather troublesome to get water from my "local" fish store, which is about 30 to 45 minutes away :cry:. I don't know much (if at all anything) about an RO/DI unit, other than the fact that it purifies water. I was wondering what I need to operate a unit such as this, where to find a descent priced unit, and how it works. I have noticed this thread on the Talkingreef forums: http://www.talkingreef.com/forums/general-marine-discussions/4688-choosing-ro-unit.html but it does not answer the questions I need answered. Also, what is a TDS meter? It appears that this would be helpful and would be a part of the answer to my first question. As a note, I have a 55 gallon tank (without a sump). Any and all help on this topic would be much appreciated. Thank you in advance.

first off welcome to Talkingreef !!! well i would go with ro/di for sure in a reef tank. I like this model from Seahorse Source (http://www.seahorsesource.com/cgi-bin/shop/detail.cgi?id=525104) its a very good model and easy to use. it also comes with a tds meter which means total dissolved solids. the lower ya can keep the tds in the water the better your tank will do in the long run. the only issue is that ya need to treat the water and raise the ph and such to keep from playing havic on your reef. which I am sure you all ready know.

i would get the biggest that you can afford right now unless you never plan on upgrading to a bigger tank. a 75 GPD system should do just fine for you. try these guys for a good price and great customer service www.buckeyefieldsupply.com. i met them at a frag swap last year and i have to say that i was very impressed.
the house water passes through carbon, sediment, ro membrane, and a deionization chamber. each chamber removes TDS's from the water and purifies it. all you will need is water into your house, and a Y that screws onto your cold water supply (i use the washing machine supply). it literally takes about 5 minute to install a RO/DI unit.
a TDS meter is used to measure Total Disolved Solids in the water coming into and going out of you RO/DI unit. i say into AND out of because i use a dual TDS meter (the best ones IMHO).