Bit of a long read.
We had a nasty wasp problem in our pool. Hundreds a day would visit. At any given point you could count at least 20 just sitting on top of the water. Menacing, creating a nuisance, stealing our water to build a bigger wasp nest somewhere else. Removing a nearby nest wasn't exactly feasible. We live in the country side in TX and tracking down some wasp nests on some acreage filled with thorny trees just isn't feasible. In other words, the wasps were coming from far away and cannot be stopped. Unless if maybe I burned down every tree and piece of brush on my property. But I don't like going to prison for arson and I like my trees. And I bet even if I did that the wasps are still somewhere waiting.
So, we gave this a try. Here's my experience and recommendations.
First off. Don't expect this stuff to work instantly like some magic potion. Not how it works. Follow the instructions. For us the problem was severe, so we followed the severe wasp problem instructions. Maybe went a little overboard with using the product per the instructions. What we did was use the garden sprayer method with "eh good enough" amount (maybe 2oz) dumped into the sprayer, probably a little more than recommended. During the day time hours when the wasps were numerous we would turn the pool pump off and spray the entire pool water area covering every bit of water we could. We would leave the pump off and let the product do its thing during the day. At night we would turn the pump back on. Morning, turn the pump off, spray, repeat. For a week, every day.
After about three days the lack of wasps was noticeable. Pool water has never been clearer. And you can see it working in live action. At least we did. This stuff works by altering the water surface tension and the wasps drown. And it works fast. Like spray it beneath a wasp and watch it fall in and drown. It's great! The instructions say wasps do learn to avoid areas that are problems for them and that seems to somewhat hold true based off a lack of wasps in our pool. I did forget treating the pool for a day and saw exactly three. They all drowned quickly after treatment. Maybe some day they'll fully learn.
So it works good. That said, you need to constantly maintain your pool with this stuff. It's not a one time cure all. Maybe some day we will be able to go to a less severe maintenance schedule. But I do know for sure it works if you use it daily with the garden sprayer and turning the pool pump (and other water features) off.
No adverse effects noted from swimming in the pool either. Doesn't make the water weird. Seems harmless to me.
Overall; we're fans. Our pool maintenance guy even was surprised by its effectiveness and will probably be using it in the future on his customer's pools.