Mike,
I was buying water from Pet Mart because it was convent for me; however, I had a large algae problem. I suspected the water and I started to ask Pet Mart how they maintain their water filters. The employees could not answer. So I figured I needed to shop around. I called about 6 LFS and the only store that I like the answers was Fish and Other Itchy Stuff. I started buy only water from FAOIS and about 6 months later I had the algae under control. One of the stores I talked to said they did not change the DI often because it was expensive. Did I really want to buy water from them? At least they were honest.
But like Rob said for a 210 G you need to buy our own RO/DI unit. I am convenced it will save you money.
On the Purely H20 units, I ordered one on June 30 and still have not recieved it. Sounds like they are still having some issues. I hope I get my unit soon.
Chris