whats the diffrence between RO and RO/DI

[fishfreak83]

wanting to know what kind of water system i need but what it the DI and do i need this?

 

[leeweber85]

Ro is reverse Osmosis. DI is Deionization. DI is usually the last stage to make the water extra pure but it needs changed often. If you are going with an SPS reef then yes, you want the DI.... if it's just softies or FO then RO should be enough.