The drain pipe and trap on my bathroom sink are made of plastic, and every four to six months I find that it slows down. When I disassemble it, the pipe walls are coated with maybe 1/8" of disgusting brown and black slim, probably fungal in nature. I end up having to shove paper towels through the pipes, which pushes out the slim in a stomach-churning sleeve-shaped blob.
Is there a product I can use to prevent this, or to clean it up when the drain slows?
My sink is cultured marble and the drain itself is stainless steel, so I don't want to damage them.