I've recently been fighting a pretty bad algae issue and finally have it under control (I hope).
When I vacuum the bottom of the pool, I'm sucking up quite a bit of algae. The return into the pool gets pretty green and cloudy. I'm concerned that perhaps the filter (Waterford JASL20) is not working properly. I assume that if the filter were working properly I wouldn't get anything, but clear water for the return.
I did disassemble the filter to make sure there wasn't anything wrong with the sand. It looked normal and there was a consistent layer of algae on top of it. I didn't notice any type of channeling either.