well, i've dipped a couple times, and i've gotten some ... things... out of this rock. some were amphipods/copepods. what i'm concerned about are the little white things.
they are about 1/8" long, maybe 1/16 wide. white body, black down the middle, broken up into two segments. they swam, didn't crawl. and did not immediately die in fresh water. i'm assuming flatworms, since i cannot find any isopods that resemble this.