White Planaria flatworm. These flatworms can quickly multiply in number and, as you will soon learn, can be dangerous to other members of your aquarium especially shrimp, snails and their eggs. From a veteranarian, Fenbendazole. It will eradicate a planaria infestation in just a few days. It’s like a planaria nuke! The dosage is 0.1 gram for every 10 gallons. So a 60 gallon tank would need 0.6 grams of Panacur C. A gram scale will make measuring this amount easily – Then sprinkle this powder into your tank.
Remove as many of the dead bodies as possible with a siphon while performing a water change.
I don't have pictures of it as I have only seen 1 so far and haven't seen it since, mine is defenitely not White Planaria flatworm as it had tiny legs. It looked exactly the same as a caterpillar but see through and it could swim kind of by floating around in the current as it released itself from the back wall.