Call me crazy....When my .2 acre forage pond was very low this spring, probably only 4' deep, 10' across and 15' long, I witnessed a school of FHM attack and completely devour a cottonwood leaf that blew off a twig and into the pond. I had been feeding them pellets regularly to that point but had skipped four days and was about to throw pellets when I witnessed this. They were apparently ravenous but looking for anything touching the surface of the water.
I thought I was hallucinating, but they entirely consumed the leaf. I had never heard of such a thing before, and am somewhat embarrassed to even post this as I realize it sounds unbelievable. Barring a flashback, this indeed happened, and would lend some support to the hypothesis they would also graze on FA.