I'm not small, my fishtank is. I have one 45 gallon tank, so my water needs are small, except for when I'm doing large water changes. Generally, I need 5-10 gallons a week, with an occasional need for up to 20 gallons a week. I'm tired of going to Wal-Mart for my filtered water. I'd like to get a water purification system, and expect that I would hook it up to the garden hose spigot when I need to make water. I've looked at the Air, Water & Ice web site and see the "Mighty-Mite" and the "Compact Reefkeeper". Besides the $40 difference in price, what are the differences that would recommend one over the other, considering how little water I need and how I plan to use it?