I just finished up some diagrams of the most-used screen installations. The overflow-feed is good because it usually has a very large flow capacity, but, you can't turn off the return pump for too long or the screen will dry out. Also, pulsing the flow is not easy:
The pump-feed below will free you from the return pump, and makes it very easy to pulse the flow using a timer. But the pump must be able to deliver 35 gph per inch of width of the screen:
The sumpless-feed (or "bucket"), which was the original design, is how you get the screen up above the tank. The pump in this case goes in the tank itself. Also, the walls of the bucket let you flow more without worrying about water spraying sideways:
Take a look at Borneman's surge device. A simple flush system like that, combined with the scrubber, is a relatively easy fix and provides lots of water motion, too.
Yellowing of the water: This is due to cleaning or scraping the screen while the screen is still in the tank water system (i.e., "in-system"). When you break algae strands, they release their chlorophyll related chemical contents, which drain downwards. If your screen is still in-system when you clean it, it drains into your tank system water, causing yellowing. Another cause of yellowing is not cleaning your screen at all. Solution: Clean your screen at least once a week, and do it by taking it to the sink and running tap water over while you clean it.
Anybody here in the Los Angeles area have N and P problems, and want to test a bucket? My acrylic scrubber is getting ready to be functional by itself, so I'll be taking the bucket offline in a few days. This bucket has an original pre-grown screen from IA, and now is almost completely covered with real red/brown turf. It has four lights instead of two, and it also has a fan sitting on top. Comes with pump and timer too.
If you have high N and P, and you are willing to test N and P every day (I'll supply the Salifert kits if needed) and write it down in a log, then you can borrow it. Would be just a loan though. PM me if there is any interest.
jski711 on the RS site says his scrubber fixed up his pH:
"my ph was dropping too low because i wasn't running my skimmer. the skimmer would help get rid of a lot of the co2 that was comming from the effluent of the reactor into the tank. so i turned my reactor off and i couldn't run my skimmer because of a medication i put in my tank, the skimmer would just overflow with bubbles in a matter of seconds. so i was running no skimmer and no reactor for about a month and a half. then after installing the scrubber i noticed that my ph was on the rise and has been high sometimes 8.5ish. so i figured the extra co2 from the reactor would bring the ph down and also help with micro growth. no more ph problems, im amazed at how much this scrubber has raised my ph. again awesome idea santamonica!!!"