I have a client that has egg size to fist size decorative rock (like the color of pea gravel) lining the bottom of his 1 year old pond/waterfall. I did not build the pond. The water is crystal clear, but there is sediment that rests on the surface of the rocks. I've tried vacuuming the rocks, but it only seems to clean the top of the rocks and not the sides. Actually, turning the rocks over made a big difference....the bottoms of these rocks were clean, but I don't know if the dirty sides, once turned back over again, would be clean next time. I know I could drain the pond and rinse the rocks, but there are about 12 large Koi to contend with and this guy wants his pond clean all the time, which would mean draining the pond every month. I don't think I'd be building up a suitable ecosystem within the pond if I did that. Is this guy expecting too much? I'm using a muck vac, should I get an attachment that fits into crevices or a better vac? Dang, I spent 3 hours vacuuming a 1500 gallon pond and I didn't feel as though this pond was as clean as he wanted.