Anybody tried a gravity feed set-up for circulation?

[Chin_Lee]

That would be great if you can set it up but like stated, you will get a lot of bubbbles if you use a durso or open pipe in your overflow.
BUT................ I think if you use the Herbie method where the flow down is restricted to point that it creates an equal input and output from the overflow, you may be able to achieve this without the bubble problems.
Check out the following links and maybe get in touch with CHAD who posted a pic in the second link.
Good luck
http://www.canreef.com/phpBB2/viewto...ghlight=herbie
http://www.canreef.com/phpBB2/viewto...ghlight=herbie