Looking for a reliable plug and play ATO

[lastlight]

Another vote for Tunze. Have owned two and will never run a tank without one.

[mike31154]

If you have the room and want to keep it simple, gravity feed from a raised container. Either use a mechanical float valve or a dual tube set up to control the level. Another advantage is that it's not affected by power outage. Of course a power outage brings with it all kinds of other issues....