Overflow question

[Joe Reefer]

What kind of overflow are you talking about? U-Tube or C-Siphon style.

If its a C-Siphon you connect a powerhead or aqualifter pump to it and it sucks out excess air trapped in the siphon preventing failure. I think most u-tubes dont have this feature.

[TheReefGeek]

You can do the same thing by installing an air-line into the top of the u-tube. But you are right, most do not come with this, and they are not necessary like they are with c-style ones that more prone to collect air and fail.

I assume his is a u-tube, seeing as he asked how the tube on top works.