Change of water?

[RADIOACTIVCORAL]

What would be the maximum amount of water percentage we could possibly change out of the tank? I have a 55 gal and was considering purchasing a ro/di filter and would like to exchange the maximum amount of the water as possible.

Also, anyone have any suggestions as where to purchase? or what amounts of gallons/day should I look for? All help is appreciated as I have been trying to read up on it a lot but everything seems like it will be better then my current methods, so I am a bit confused on how good I should go.

[Mike31154]

RO/DI system is a wise investment for this hobby. My water changes are about 30% every 15 to 21 days. Many have a more frequent but lower volume change schedule. I think my method is considered old school but so far it's working fine for me. I'd recommend not getting too carried away with the first water change with RO/DI water. 25 to 30% is probably a good start. You can always do another similar volume change a week after the first. Changing much more than that at one go might be overkill and could be a bit of a shock to your livestock. Very large water changes are usually done only in the event of an emergency where something has gone terribly wrong.

As far as which system to get, there are a number of sponsors on this site who offer very good units at similar pricing. The most popular seem to be the 75 gpd systems since they have a very good rejection rate and production is fast enough for most systems. Should be fine for your requirements on a 55 gal tank. Have a good look at each system offered and the accessories that come with it. Often the significantly lower priced systems have lower quality RO membranes and pre filters. They will also not come with items such as TDS meters, pressure guages etc. You should be able to bag a very good quality system from any of the RC sponsors for around $200.