I think the key here is how the stuff swirls in curvy patterns as if it landed on the surface and is following the motion of the water (I have aeration) instead of growing from within which I would think would look more ubiquitous. (alike throughout)

We've had several inches of rain in the past few days that might make a difference in appearance. I think I'll collect a bucket and take more pictures. Thanks, all!


Bennie
LMB, HBG, YP, CC, FHM, located SE Michigan
1/3 acre 8-9' deep, aerated 24/7 1/4 hp rocking piston