I have had my surf 2 almost a month. I have noticed very slow growth, two weeks ago I put in a hair algae mat and some chaeto from my other tank and the algae has done well but the growth on the scrubber surfaces is still slow with a few of the stands now showing a tiny bit of green. Condition initially were 1ppm po4 and 20ppm no3. I have wondered about increasing flow through the scrubber, similar to the concerns Floyd has so I thought I would post. I recently made a couple modifications to the surf 2, nothing that can't be undone, but I wanted to try it out. I took a maxijet I had lying around and ran a hose to one of the holes in the bottom of the scrubber to increase flow. I also added 90 degree elbows to the air line intake on the bottom as the water was pushing the bubbles out, and the 90 degree fitting solved that problem. With no permanent modifications there is now quite a bit of water going through the scrubber and seems to be working well. I did raise the lid a bit to accommodate the increased volume leaving the scrubber. I would have liked to use a powerhead that sucks air in for even more bubbles, but I had this lying around. I can always change this back if it doesn't work well, but I think it should give an improvement. I have not had this going long enough to evaluate if there is increased performance. I have a flow control valve from my old tlf reactor that I dialed down the flow a bit. Hoping to find a sweet spot.