hang on overflow?

[_range_]

I saw this mentioned in a tip on advanced aquarist, but no information about it. Running a 20gal long and I'm looking to set up some kind of overflow and sump/refug but I want to stay away from drilling. Anyone know how a hangon overflow works, or another way I could rig it up?

 

[Fatal Morgana]

CPR among many other makes hangon overflows. Some people just use an U-tube and siphon the water off. Check out some manufacturer's website.