Sounds like there's a lot of misconceptions out there... Just reading the answers given. Let's review shall we
Tubiflex worms, are a pale brown worm, who generally inhabit very nasty waterways. The parasite/disease etc concerns come from tubiflex we saw years ago, some of which was of 'questionable' quality. These guys die and go rank very quickly when removed from water, leading to the now famous 'Tubiflex will kill your fish'. Though you may see some real tubiflex in stores - it's generally fallen out of favor with the aquaria industry. You will not get Tubiflex worms as a live food unless you collect it yourself (And remember the water conditions it likes - polluted). But several manufacturers use the tubiflex name on other types of worms.
Bloodworms, are a reddish black 'worm'. _Should_ be midge fly larvae. You will not get these guys live, frozen / freeze dried only. Since they are fly LARVAE... Good stuffs - not many fish will turn up their nose at these guys.
Blackworms / California Black worms (CBW), are black and they're a worm. These you will get live! You keep them in a tub of water in the fridge, do a water change every other day (Some say with RO/DI water). Like bloodworms everybody will attack these. Some discus and angelfish breeders (among others) will feed these almost exclusively once weened from BBS, as they're great for putting weight on fish.
Andy