How to reduce bubbles from drains sump. Help..

You have to be VERY careful doing it and tune the length just right but you can thread a length of 3/8 nylon cord through holes on the side of the Durso to reduce the drain size of the pipe into the sump. I did this to both weir drains on my 110g back in July '09 when I filled it. No floods to date. Trying a knot holds the cord in the pipe because it won't fit through the hole. If I had it to do again I would have drilled a third hole in each weir for a second stand pipe/overflow. I've had to adjust the length of these 'drain tails' four times (sump modifications) but am going to continue as it's configured because I have zero drain noise.

Coudnt I just put a bulk head on that uses a smaller hose?

I stumbled across this browsing youtube, seems so simple yet supposedly silent, no bubbles due to allowing only what your return pumps back. An even exchange. You could add a ball valve and adjust how much drains but without a back up it might actually overflow.

http://www.youtube.com/watch?v=6Pv3u0Sa1tk

Interesting. I have two overflows. Wondering how that would work.