Question on Circulation between two tanks

[rossb]

A little confused about the hole to stop the syphon. Is it below the water.

The hole is drilled about an inch above the water line. If the pump ever stops the hole immediately stops the water in the tank from syphoning back to the lower tank.

Next question is how did you drill into the aqua clear. Hole saw?

I used a 1 1/2 inch hole saw. If you do this make sure you clamp a peice of wood behind where you are drilling the hole and realy hold onto the aquaclear unit. I used a cordless drill and it worked quite well. Also make sure you know where the water level is before you drill. If you drill too low the water level will be low in your tank. If it is too high...well its a bad thing. I think the bottom of the hole I drilled was 1/2 inch below the desired water level.