Those little critters look like little snails. As far as I know, it shouldn't hurt the angels if they are eating them. Not sure about kuhli loaches, but yoyo and clown loaches eat them too, so perhaps they'll have a tasty treat
. Bettas will eat them too I think.
PS. Y'all (yes, I'm from Alabama where we use words like "y'all") stay up way too late. Lol. Apparently no one else on here has 8am classes they have to show up to