I do not have any fish small enough to be bothered by him and I don't have any shrimp. I will keep an eye on my hermits and snails tho.
muchas gracias.
it might be the shell of a hermit crab banging on the glass as he hustles past. I heard the same sound for a few days and it made me crazy. I went hunting for the source and it was a little hermit's shell tapping.