I have a 10gal low-tech with bts, rcs, java moss, anubias, and java fern. Substrate is just aquarium gravel, and I do 20-25% changes every five days. Temp. is 72-74F, and all readings are fine. They're fed half a Shirakura tab once a day for three days, and then one day off - they finish within 3 hours, or I remove the rest.
But... I've started noticing these tiny worms - they're white to beige, about 6mm long, and about the thickness of fishing line. They'll just float, and then all of the sudden go into convulsions - I'm assuming that's how they move. Mostly, though, they just burrow into the sponge on the filter. I've been watching them for a couple of days trying to figure them out, but now I noticed they're attaching to some of the bts, just under their tails. I watched one this morning, and it actually let go of the bts and floated to the bottom. I'm assuming it fed, and then released when done. Oh, and I haven't noticed any on the rcs. Any ideas??
I snapped a picture with a basic camera, and you can barely see one hanging under the tail, and one sitting on the sponge.