steve8855

Ya know... they all basically work the same with a small pump that's controlled by the switch. Double float switches (or triple... or quadruple) are better for redundancy and safety.

If you're not planning on buying a JBJ or hooking one up through a controller I would at least go for a double float switch to keep your ATO from overflowing your tank. The upside to a JBJ or one controlled by a controller is the reduced risk of it sticking and emptying your entire ATO into your tank and dropping your salinity quickly. Some people keep a float switch to turn the pump on, another to shut the pump off if the water gets too high (for instance if a float switch sticks). Some use a third to shut it off if the ATO water is running out. A forth... awww heck put it on the tap at the bottom of your mug. They have endless uses. :-)

What does that cost?

Like six bucks... but it increases your other expenses significantly. Lol

Maybe I should build one!

I was talking about the kit pictured above.

$80 and 100 for te two float one

You can get a nice DIY kit from Aquahub.com for $50. I did a full write up about my experience here:
http://www.reefaddicts.com/entry.php...Top-It-Off-kit

Steve,
I followed Marc's advice and purchased the aquahub kit for $50. In about 30 minutes it was up and running. I also bought other components from them... made a few dumb mistakes and they really took care of me... giving me credits for my own mistakes on future purchases! I cant say enough good about them.
Jim