Steve good post here, just stumbled across it. I like your theory of SMB fry hanging with the tadpoles...makes sense to me.
I'm having my worst bloom of FA in my pond historically - water is gin clear to the bottom in 9' depth and the Sago and American pondweed also is blowing up and deeper than usual. Sago should start dying back and giving way to the American here in the next couple weeks, and the arrowhead should start popping too. I love the clarity, and think the FA is now dying back, but it left it's green carcass all around the margins of the big pond I'm trying to rake up little by little. I am collecting it after it dries to use as a % addition to my growing medium next Spring. I think my peppers and tomatoes will love it - maybe it's finally a benefit of FA!