For your relatively small set up, I'd consider a gravity fed ATO if you can swing it and have room for an ATO container at a slightly higher level than your sump. All you'll need then is the container, some tubing and a mechanical float valve, no electricity at all, particularly any kind of household voltage running through a light duty float switch. Because I don't have the option of elevating my ATO above my sumpless DT, I use a variation of the gravity feed option using an air pump on a timer pressurizing a glass wine carboy. The positive air pressure in the carboy moves the water into the display through a mechanical furnace humidifier float valve. So a little bit of electricity involved in running the air pump on the timer, but nothing electrical near or in the water. Actually not unlike the Aqualifter concept except using an air pump instead of pumping water thru Aqualifter. Don't have to deal with the electricity thru float switches though. I get nervous around 115VAC too close to the water, cringe when I see photos of heaters fully submerged, control head, cord & all. That's just an accident waiting to happen.

Great idea Mike. Should be quiet too. I'll consider a gravity ato... but i just bought a new controlller... :)

Thanks for the aqualifter Dave.

Still looking for a vertical float switch - need one in the next few days. Thanks!