Too much flow through algae scrubber?!

[WhiskeyCoffee]

A little while back I made a super simple algae scrubber consisting of a 70gph pond pump and some vinyl tubing. I literally made a slight in the end of the tubing and inserted some of that sewing mesh into it and used zip ties to hold it in place. Many people said it was not enough flow however in one week I was starting to get some brown slime appearing. Here's what it looked like:

The other day a friend gave me a Rio 550 pump and I decided to make a more legitimate algae scrubber out of PVC. I knew 550 was going to be a lot of flow so I added a ball valve right before the slight for mesh and another ball valve right at the base so I could divert flow. I even tried to add more elbows in the diverter to reduce flow. Even will these valves restricting and diverting, it turned my 20g sump in a typhoon.

So... Where is the middle ground? Is the 550 too powerful or how can I better restrict the flow? What kind of gph pump should I get instead?

 

[wopadobop]

First things first . Did you rough up the screen?
Secondly you will know when you have enough flow when there is a sheet of water covering the entire screen. From the looks of it you are feeding the scrubber with a 1/4 tube? Problem with is it’s flexible and will collapse down on the screen and make dead spots. Run a piece of pvc through a table saw will make an 1/8 inch slot. Then cut some pvc pieces about 1/4 wide . They will act as clips to hold the screen on. Recommended I believe is 20 gph per inch of horizontal screen. But it’s been a while.