the21kid said:sorry but forgot to address something else in regards to your question forman. The number of stages doesn't have much, if anything do to with how much water the system will put out. The more stages the more "pure,"if you will, the water that will come out. If you are comfortable spending what is asked for on Ebay I would go with it. I did some searching, as I bet you did, and noticed that the RO/DI units specific to aquariums are much more costly and produce less water in the same amount of time.
Might be a little overkill since it is a 6 stage RO so you will probably need to add some trace elements back in.
the21kid said:I did some quick searching and the only 3 or 4 stage units I could find were specific to aquariums and costed much more than the 6 stage you are contemplating. They also averaged and out put from 24 gallons a day to 50 a day. Adding the trace elements back in is very simple and effective. I am not sure how big your tank is or what quality tap water you have currently but I would go with this system. Hopefully this helps and I will let you know how mine turns out. Good luck and sorry for the confusion
Adding the trace elements back in is very simple and effective. I am not sure how big your tank is or what quality