White fuzz growing in vinyl return hose??

I set up a sump about a month ago and lately I've been having issues with my return hose... I used a vinyl clear hose and a 225 or so gph power head to return water. I limit it with a 1/2 in ball valve.

When I first installed it, water would jet out of it until I turned it down with the valve. Then I noticed that it mysteriously increased in power so I had to turn it down. Then it did it again, and when opened the valve all the way, the water didn't jet out anymore, just went up a little bit.

The only thing I could think to be causing this is the white fuzzy stuff growing in my pipes. I assumed it was beneficial bacteria? I scraped some off and it's not that thick but it's all along the inside. My fish seemed to like it when some fell in the tank.

Any ideas?