I am wondering if the brown sludge in my pond is algae, i have a small pond,135 gallons with a 35 g spillway . I started out with clear water but lately the water is so dark I cant see the bottom, i did a water change last week and it was better but a couple days later it was dark again. I scrub the brown stuff and a foam filter is catching it but it gets clogged. should i remove the foam since it isnt reaching the uv light with the foam on? It did not come with the uv filter but i thought it would be better to use it. i have 3 small koi and some goldfish. i don,t overfeed. Another concern is a big mulberry tree that is dropping berries in my pond. It seems they are disintegrating and leaving residue. does anyone use the pond vac they sell that hooks up to a hose. i dont know what to do, i started the season with strig algae and cleared that up with barley and now this?? any suggestions would be appreciated.