This morning when I was feeding my frogs, I noticed a greenish grey worm/nematode thing crawling around on the soil. It was about 1/2" long and maybe 1mm thick at the widest point. It crawled around on the surface for a few minutes and then disappeared. The substrate is about 4" of dirt jungle mix dirt and coco-bedding. I figure it must have come in with one of the plants. It's still mostly bare dirt while the moss grows in. Is this some kind of parasite? Will it harm my frogs?