I discovered two critters recently that I can't identify.
1 - very thin dark red worm in the gravel, right next to the glass. It was about 2.5" long, and maybe 1/16" wide.
2 - Behind my mushroom rock, there are three things as thin as a hair, with short bristles all over them, and white in color. They come out at night from the substrate and just wave in the current, but remain attached somewhere under the gravel.
Any ideas?