Had a pond for 10 years and I've NEVER had such trouble. It's about 800 gallons. I got rid of my filto-falls and installed a filter with uv light that's rated for a pond over 1,000. Just a few goldfish that I have not fed this summer due to water problems. OK, it's been HOT this year and I made a stupid mistake and thinned my water lilies too much so I have lacked coverage. My ache has been floating algae that forms with the sun looks like scum and no amount of scooping will prevent. I do not have runoff water washing in and I do not have a much sediment I the bottom. I have vacummed it several times. I've used lots of microb lift . I've added baking soda. My plants are starting to slow down of course but my water hyacinths have wasted away. I sure don't want to repeat this next year. Any water professionals out there ? I know the lack of shade was a problem but I'm thinking other water balance issues.w. Thanks Charlotte