Here is one brief link that may help, http://schools.ceh.ac.uk/advanced/freshpoll/freshpoll10.htm it shows a picture of a flatworm, (planaria), a roundworm, (nematode) and the freshwater earthworm, (oligochaetes) What I have seen in my tanks is probably nematodes. They swim like snakes, and look like a small skinny red worm. Robert Hudson www.aquabotanic.com ------------------ To unsubscribe from this list, please send mail to majordomo@thekrib.com with "Unsubscribe aga-member" in the body of the message. Archives of this list can be found at http://lists.thekrib.com/aga-member/