There have been a few folks on the site who have built some and ran them. Unfortunately most have not really been around much. I'm actually planing for one on my current build project. I've been doing a ton of reading on them lately and believe that they can be a remarkable asset to a reef tank.
There does seem to be a bit of science involved though. A little more than just throwing together a screen with some lights in order to keep them running very effectively.
Here's a link over to the scrubber site, it's nothing but guys who run scrubbers. Lots of good info, pics and results. This here is the page to the basics of setting one up for your tank and Q's and A's.
http://www.algaescrubber.net/forums/viewtopic.php?f=9&t=68
Been following some threads over there, guys are trying to nail down the specific color spectrum's in regaurds to running LED's to target specific algae growth. Just starting to see some pretty interesting results.
I'm building mine directly into the fuge section of my sump. Will have it's own pump feeding it with two small panels of LED's on either side. I ordered some extra stiff screens #7 count that should be here on monday.
