Hmm interesting. I was thinking of adding a barb or a small valve at the piece that goes over the tank's side to make filling the tube easier. Thanks for the warning about degassing. I suppose if I have CO2 up really high I might have to be more careful with that.
Can you make a diagram to show what you mean by this? I don't understand how it will work.
You could also get rid of the upturned skimmer portion and have the intake under water with a sponge plug, this cuts down on the amount of stuff that can plug the overflow. The level of the 180 with the air hole will set the water level in the tank.
Also, in your experience how often does the overflow design (like in the picture above) get clogged? Or does it ever get clogged enough to stop flow?