Are you from California  GuppyAdict? I think they banned tubifex worms (which often come from very polluted waters) for health reasons. And maybe because they like to pass laws banning things. ;)

Black worms (aka California Black Worms) are a different species, from different waters. They have been criticized if grown in water near fish, but other wise should seldom carry diseases.

Feed a few at a time from a worm feeder or in a little pickle jar.

Rinse and rinse them until all dead stuff is gone when you first get them. (A gallon wide mouth pickle jar is useful here.) Store them in the refrig. with water just covering them. Rinse every 1-2-3 days.

For culturing or just learning more about them see:

http://www.carolina.com/tips/worm/worm.htm

I wouldn't bother trying to culture them. Too much work and very little return for your invested money and time.

One can buy them through the Net, but that involves a lot of money and too many worms for most of us to use before they die. I prefer to get a portion or two a week from my LSF. It encourages them to carry live foods too. :)

However one worm place both shows how they raise worms and more importantly sells a great worm keeper. I highly recomment the worm keeper. It also slides unobtrusively in a refrigerator shelf. ;)   (Dear Santa again!)

http://aquaticfoods.com/farm.htm

Blood "worms", black worms and cultured white worms are very rich food. They are best fed to female guppies and youngsters once in a while. Feeding older fish a lot of worms can produce obese guppies!

It's pretty funny to watch!!!

I do thaw them first in a little water from the aquarium.

I've never tried tubifex worms.  One kind of wormy food is enough for me.