Here's some threads about the gate valve mod. I don't think it's going to help with micro bubbles though, you might need more baffles in your sump or a filter bag for the output.
I have done it on 2 Euroreefs and it gets rid of the sponge (which might actually make bubbles worse) and makes adjustments easier.
Try a search on RC as well, ASM club and Euro-reef club.
http://www.asmskimmer.com/mod1.htm
http://www.canreef.com/vbulletin/showthread.php?t=28090
http://www.canreef.com/vbulletin/showthread.php?t=28267