I have been finding LOTS of these little guys, in the last week I have probably taken out 100 out of my 20gal

Tonight while feeding I picked out a few. They kinda look like sundial but I'm not 100% sure not taking the chances until I have a perfect ID
I grabbed these guy for photos and I dropped about 10 and there was at least another 10 I couldn't get to ....in 5 minutes
Any Ideerers?