Dave,
"Uniquarium" makes a skimmer that is a round acrylic tube with a collection cup on one end. It is made to be powered by a Rio 600 venturi that injects the water/air mixture through a hole in the side. This acrylic tube fits into the space for the SeaClear airstone skimmer. It takes some work, but it fits. The rio 600 goes on the bottom of the skimmer area, pointed upward into the bottom of the skimmer tube. You'll need additional airline tubing, as the tubing included with the Rio isn't long enough to reach from the bottom of the skimmer area to the top (ie, to the air). I attached a tetra luft airpump to give some additional airpower to the skimmer, and it worked better than the the airstone skimmer that SeaClear sells (and I didn't have to change the wood airstones every month). The downside is that it's hard to get to the rio to clean it or perform other maintenance. The skimmer area is tough for even someone with small arms like me to reach to the bottom of...
I'll try to diagram the bioball area that I've turned into a 'fuge...not sure if this will work...
.|..|..............................|
.|..|..............................|
.|..|..|...........................|
.|..|..|...........................|
.|..|..|.........|........|.......|
.|1|2.|..3 ....|..4 . ..|..5 ..|
.|..|..|.........|........|.......|
.......|............................|
Okay, 1 is the skimmer chamber - water flows across the bottom of that chamber and up and over chamber 2 into chamber 3. There used to be a drip plate across the top of 3 and 4, and the water overflowing from 2 dripped down into bioballs in 3 and 4. Water flows along the bottom of 3 and 4 into 5, where the main system pump pumps the water back into the tank.
I took a piece of acrylic and glued it over the opening at the bottom of 4, between 4 and 5. This allowed me to put 3-4" of sand in the bioball area. I drilled 1" holes in the dividers between 3 and 4, and 4 and 5, about an inch from the top. This lowers the water level in this refugium area slightly, but helps keep stuff from running across the top of the water from 2 and overflowing into 5... it helps keep stuff in the refugium. I put a 15 watt NO fluorescent Tr-phosphor bulb directly above this refugium area, and there is some spill over of light from the VHO bulbs.
Now, to see if it gets all messed up when I post...
Kevin