Hi all, great forum with lot's of great tips. I'm new here and have several threads. I have a 5000 gallon pond with a waterfall and skimmer. The pond is about 4 years old. I have managed to keep water fairly clear this year but have struggled with "carpet" type algae or sludge on every rock service. Large rocks, medium rocks and all the small stones. I have tried all kinds of muck and sludge products but to no avail. I do have a pond vac but looking for what others have done to tackle this problem without constantly draining a large pond. Thoughts?