We got the JBJ one, was about $100. It's nice not to have to top off every day. In our 125g, it was about a gallon and a half a day we'd have to top off. If we forgot a day, the pump would start to pump air into the tank. I think we fill up the 10g reservoir about once or twice a week. You need to make sure that the amount of water in the reservoir could not be enough to overflow your sump (or tank) under any circumstances, in case the pump sticks on. It's not a good idea to hook your ATO up directly to an RO feed.