herbie setup

[soapy]

Originally Posted by Myka

The required distance is a direct relation to how much flow there is. The main drain needs to be low enough that it doesn't create a vortex at the surface and suck air in. I make the main drain as high as possible. The lower it is, the more water drains to the sump when the return pump is off.

Exactly. It is also good to have lots of capacity in the return section of your sump to handle these level variations so water doesn't back up and mess with the skimmer and to give a little extra leeway so there is less chance pumps run dry and burn up if there is a problem with the ATO or reservoir or whatever.