OCLT good…but algae still in pool

I sleuthed last night. My skimmers have two fittings for pipes. One is connected, and the other is not. Its just a cavity. Well, one of them was FULL of crud.

The fountains are stone overflow bowls. Aside from scrubbing them, anything else I can do?

Do I have to scrub the Pump filter bucket cavities? The main filter housing?