I'm planning on getting an RO unit, but don't really know much about them. Are they all created equal? What's a good brand for the price? How well do the coralife ones work? (seem like the cheapest) Any advice would be great~
I bought a full on Typhoon III to help with both planted and reef tanks, for the clear, vertical DI cartridge and all the extras. For a planted tank alone, the ~$100 4-5 stage units on ebay are fine, they're all made from the same little plastic parts by different folks, the filter membranes etc can differ a bit in efficiency but in FW, a trace of left over minerals is going to help more than it'll hurt.
If you have SW reef tanks, get a unit with a clear, vertical DI cartridge and a fast flush, test the TDS periodically.
It seems that the most popular RO/DI units are SpectraPure (expensive, considered the high water mark I think) and AirWaterIce.com - less expensive, value point. Units off of E-bay are usually fine too (and the least expensive), especially if you are just doing FW as mentioned above.
Another follow up question, does having DI after the RO do anything bad for planted tanks? I know it basically makes the water unhealthy to drink (more so than RO), but will it affect planted tanks in any way?
I've really been looking at the typhoon III, it seems like a great unit that's a much better value than the Coralife and Seachem ones.
No problem using DI in Freshwater - except that it is kind of a waste of money (will burn through your DI resin faster). The Typhoon III has an RO out and a seperate DI out - so you can have it both ways. I use mine with the RO out for my FW tanks and the DI for my reef tank.
Never heard of DI being unhealthy to drink either, tastes strange and is another waste of money, but I'm still alive.
You still get enough minerals etc from food and other drinks, if that's what people mean by it being unhealthy. AirWaterIce claims pure hydrogen ions metabolize faster or hydrate you more efficiently, or something like that.
Ya - no problems with DI - people just don't like the taste - the Typhoon III takes a drinking line out of the RO (before the DI) and puts it through another carbon filter before bringing it up to the little RO faucet.
There are also taps for RO and RO/DI for fill containers, etc.