yes the circulation on the grotto shelf is not great and it's probably in the shade most of the time.

As for the other spot it collects is on a step from my baja shelf into the pool and this is right near the spa spillover so I would think circulation right here would be excellent however it collects like crazy right there. The sweep can't get to it. I have to brush it.

I might try the algaecide and I am keeping the chlorine level high right now to see if it will prevent it from coming back.

thanks,
-- john