Are those really what tubifex worms look like? There's lots of controversy and debate behind their usefulness as a food and their simularity to a blackworm. I grow blackworms at home in a container to feed to my turtles and corys but the lfs I buy them from (when I'm running low or or kill my coulture because I'm lazy and cleaning their water is hard) sells them as bloodworms.. which they obviously are not, so when I ask the manager about it, he says everyone calls them bloodworms but they're actually tubifex worms.. also which I do not agree because my research has lead me to believe they are california blackworms. The worms I have look simular to your pic but they are darker brown except when they split and form a baby, then they are pinkish for a while. They also get like 4 inches long frequently but split soon after. So anyways, I'm against using live tubifex worms unless the conditions they were raised is sanitary. Freezedried tubifex worms in the cube form are great though, press it against the glass and it's quite a show to watch if you have some sharks or aggressive fish.