overflow question

[toolz2]

I have 2 overflows and inside has two drains one about half way up and other just about half inch above the bottom of the overflow. Question is how high should I have my water level In the overflow. If I keep it high, just below high return its super quite. But I do t fell I achieve skimming that way due to the lower drain. Being 10-12 inches below the water level.

 

[IPisces]

sounds like you have a herbie overflow system
here is some info on it.

http://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

 

[toolz2]

Thanks for the link