Mine have put a serious dent in my algae problem. As for spawning, I don't know. Everything small bolts when I get close to them .

They don't seem to clear FA all that great for me. I stocked 70 pounds in a guys 1.5 acre pond after having everything sprayed twice Then, they later added 80 large ones from another source. There is still a major FA problem.

So far, I'm not much of a believer.

I'll have more of a report after Labor Day. So far, after stocking them, and whacking back the algae chemically, it hasn't come back.