Question about "Coralife Pure-Flo II - 24 gallon-per-day RO system"

I am thanking buy and rodi unit and I do not want 50 or 100 gph would like to have a 24 or a 30 gph if they make them and do you no how much they cost . I am new to rodi water . all was use tap water for my salt wate tank .