Update on my experience treating watermeal so far. I've been treating with Flumioxazin (brand name: Propeller) starting in the Spring.

Early April: Started seeing "just a little watermeal" around the pond edges

1-May: First treatment of Flumioxazin with hand sprayer to include surfactant. Pond was about 10% covered at this point. Pond went brown and scummy within a week and slowly began to clear in weeks 2-3. Watermeal began to spread again.

5-Jun: Watermeal was back to 10-15% pond coverage. I sprayed again and the same 4 week cycle repeated with the watermeal spreading again around week 3.

5-Jul: Once again, the watermeal was back and slightly more aggressive with 15-20% coverage. I sprayed and the 4 week cycle once again repeated.

14 Aug: Watermeal was back right on schedule and we're in the midst of the scummy residue clearing once again.

I've used higher and lower amounts of the recommend doses of the Flumioxazin with no discernable difference in results. A "feature" of my approach this summer is that the pond has looked scummy most of the time. This has been purely aesthetic. The health of the pond and fish has been great with stocking of BG in the Spring (pond only had stunted LMB) and the 4-5" BG are now at least 5 times bigger and fat!

Next Spring I'm going to try Fluridone (brand name WipeOut). For my pond size the cost difference is about $90 for the roughly 4+ treatments I've done this year versus $400 for (in theory) for a single treatment in the Spring. I'm hoping the Fluridone will keep the pond looking much better all Summer long.