A pond were carpers are being bred
The last 3 or 4 summers there was a blue-algal bloom each time when the weather was at its best,
and hence swimming was prohibited for weeks...
I have a spring in my yard that had caused a big patch of mud to be in my backyard(down in the hollow), a big PITA to mow.
I planted weeping willow trees to drink it up... nope, didn't work... I got to thinking, since it's wet, why not have a pond? So I dug a 'test hole' about 3 feet deep, 1 foot wide, and watched the water level for a year. Yep, even in the hottest dryest part of mid summer, there was standing water. So I started digging a pond.
Well, the first year I got pea soup. Yuck! I tried a couple wal-mart solutions, but the damn stuff came right back. I tried scooping it all out, same results. Winter came, the goo subsided, and I got to spend some time not having to worry bout it for a while...
Then sping came. And MOSQUITOES! And pea soup. Well, I figured, go get some goldfish(carp) to eat the larvae, since they can survive in nasty water like that. Went to a pet store, bought 50 feeder fish for $5.00, dumped them in. Carrots for the pea soup...
And... the pond scum was gone in 2 weeks! This puzzled me, since the only thing I did was add goldfish...
I was at a store shortly afterwards, and saw some goldfish food on a shelf.

I looked at the ingredients. First on the list- algae. Well whaddya know, goldfish eat algae, not just bugs and stuff! Haven't had an algae problem since. Nor a mosquito bite. The pond is FULL of fish, and I don't feed them at all. Never saw a dead one yet.
Just a suggestion, but maybe more fish would help...(yeah, I know, it's not your personal pond to make those decisions).