My dad has a 23x16' Koi Pond and he uses a fish net over the pond when the pines are dropping, and again when the oaks flower. The rest he lets rot in the pond (the Koi love it I guess)?My pond is still under construction, but will be 8' diameter and 2' deep. I saw one advertised as a pond vac that uses a garden hose to provide the suction. Apparently it uses the hose water for suction but doesn't put any hose water into the pond(?) to keep from adding chlorinated water. It looked alot like a shop vac with a floor tool head on the end of the hose. My yard is surrounded by big old firs and they drip needles EVERYWHERE....
Have you asked in the cold water section?