Autoaqua smart ATO micro is what I've been running almost 2 years, it works great and has never failed on me and it's super tiny. The magnets that hold it in place could be better but they have never let go. Running it on an IM40 about 4-5 gallons a week. When it runs dry a loud beeping happens which is nice, but also annoying when I'm not home, luckily I have finally trained my wife to unplug it. Hint. When you first plug it in whatever amount of time it initially runs to fill to its desired point that sets the emergency over fill time. You can reset it by unplugging and it will choose the new time. I found that out when I had left my ATO off and made it fill the tank back up alot, thus making the time far to long to do any good. So I unplugged and reset it and it was good to go.