Hi Alan and welcome to GoY. We had to give u pin one of our ponds as a large ash tree dropped its leaves into it every year. Not sure there is a solution for you...

Rigid, fine hole wire mesh will do the trick, so long as its suspended a few inches above the water.

Great idea Bamboo - we have the same problem. But where to keep the mesh the rest of the year,lol?

Well, if you buy large rigid sheets, it can at least be stood upright against something in a not very visible spot... got a friend who stacks his behind the greenhouse when its not needed

Probably the only thing to do. I wonder where you get them.

builders merchants usually