Found this on RC -Post from RichK back in 2001 on Red Sea Skimmers (aka Berlin skimmers I think)
"After setting up a 2nd reef, for softies, I dug out the red sea skimmer. It did "OK" but never really did great. Here is what I did to make this skimmer awesome. The only parts you will need are a 3/4" venturi valve (
www.aquaticeco.com sells them) and a couple of fittings. Depending on how you use the skimmer now, these can be hose barb or FPT/MPT fittings.
Here is what to do:
1st- remove and drain the skimmer.
2nd- unscrew the hose bard fitting on the input of the skimmer.
3rd- with the tool that came with the skimmer, or a butterknife, remove the venturi cone inside the input.
4th- screw the venturi valve into the input of the skimmer. If clearance is a problem, inset a "L" fitting into the skimmer first, then screw the venturi into that.
5th-run a piece of airline from the input of the new venturi to above water line, if necessary.
6th- with a small piece of airline tubing, block off the original air input to the skimmer.
7th- fill up the skimmer and reinstall on system and turn on the pump and check for leaks.
WARNING: there will be ALOT more air flow into the skimmer, so it may turn into a small volcano. The pump used for this should be a Mag7 or equivalent. Rio 2500s don't work although a 3100 may. If a Mag7 isn't an option for you, you can simply use a Sen pump as well. You want about 600REAL gph going through the new venturi. After doing this mod to mine, I am quite impressed. I get dark smelly skimmate. Something which I only experienced on my big ETS. I few people have done this after I told them about it and they have had the same results."