Just wanted to post about my satisfaction with the A.T.O. (auto top off) by JBJ. It does what it says and my specific gravity has been pegged at 1.025 since my last water change. I cant believe that I used to add a gallon a day by hand. I bought this after my salinity got out of wack, added too much R.O. and watched my birdsnest shrivel up. Since stability is key to a happy reef I suggest this product to anyone. If yours happens to come with the buzzer turned on (it is loud and anoying) there is a switch inside the controler, all you have to do is remove the four screws on the back and flip it to off. It also has a sensor to tell you when your reservoir is low and it will not allow your fill pump to turn on. Best $100 I have spent in a while and I wish I had bought it years ago.
Update:
Hmm I heard water splashing today while sitting at my computer, thank God I was home, and my ATO was overfilling / about to overflow my tank. Gona have to keep a close eye on this....