Hi, Jeff,
I can't help you debug the issue but I can tell you the cure.....chlorine. If you have algae, you don't have enough chlorine.
While it's not that simple, it's a great rule to follow to keep a crystal clear pool. So whatever you're doing now and still getting algae......add more chlorine to the pool and keep more chlorine in the pool.
Whenever I get algae, (I am presently cleaning up a nice little bloom of mustard algae) it's ALWAYS because, at some point, I haven't maintained enough chlorine in the pool.
It helps to clean up all the nooks and crannies and clean the ladders, under the steps, etc. but it always is lack of chlorine in some way or another.