Looking for a reliable plug and play ATO
 

The return section of my sump is so small (~5gallon) that it needs to be topped up every day or the return pump starts sucking air.

I am looking for a trusted ATO that will work out of the box and preferably something with built in redundancy.

Hard to go wrong with a Tunze Osmolator...

Tunze osmo all the way.
BEST purchase I ever made for my sump.

I wouldn't consider anything other than the Tunze Osmolator on my tank. That's what it has now, and nothing else would be an option for me.

Another one for the Osmolator.

Remember what Vince says: "The Germans always make good stuff."
http://i27.photobucket.com/albums/c1...18-shamwow.jpg

Vince also says: "Stay away from cannibal prostitutes"
http://www.bestweekever.tv/bwe/image...HAMWOW-GUY.jpg

...Sorry I couldn't help myself...

But, yeah Tunze ozmo is the best ATO.

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

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....

I use 2 JBJ ATO on my 2 tank and they have worked flawlessly for a year now. Much less expensive than the tunzee which was not in my budget for my 2 aquariums.

For another option check out Blue Line's Tsunami AT1 I've used one for 8 years literally without any maintenance. No moving parts it uses air pressure.
You should be able to find one for $60-$70
Don't use the suction cup, zip tie it to a bracket.