Paul A. Ergh wrote:

No experience myself, but here's what I've heard.

I just got back from the LFS with a single serving of live black worms.
When I put them in the tank I was amazed to see a few "get away" by wiggling
into the substrate. Not sure why I was so amazed to see a worm burrow into
sand but I was.

It's a decently well reported occurance. (Search for info on blackworms,
and you'll find it discussed.)

Now I am wondering:
- can they survive in my laterite/fluorite/black sand substrate mixture?

They eat bacteria and people can grow them on a brow paper towel
substrate, so my guess is that they'll probably be able to live.

- Will they ever come back out for a little stroll in the light or dark?

Occasionally they'll pop their heads out, and if a fish is nearby -
WHAM! one less worm.

- Will they reproduce?

Yes. They can reproduce by fragmetation, so if a fish gets one half, and
the other half is stuck in the substrate, there is a chance the
remaining half will survive and grow.

- Is it good for the tank/plants like in a backyard garden?

I doubt it's bad for the tank. At the very least, it's another food
source for your fish.

- Are there bad and good worms for aquaria?

It's said that tubifex worms, since they are (at least used to be) grown
in sewage, can carry parisites. True cultured blackworms aren't tubifex,
and are said not to carry disease, especially if you rinse them in
(clorinated) tap water before adding them to your tank. At any rate,
once you've added them to the tank, any diseases they were carring have
entered the system, whether they die quickly or go on to live in the
substrate.

- Is there an easy way to harvest worms for feeding similar to the way brine
shrimp are?

Blackworms are reputed to be fragile - no grabbing with tweezers. People
suggest using toothpicks/spoons to lift them out. There are more
elaborate methods used to seperate out the live ones from the dead,
rotting ones.

Will they get cooked by my 200w substrate heating I have in this 75g tank?

My guess is that they'll know enough to stay away from the hot cables.
Unless the surface of your substrate is cooking temperature, they'll
probably be fine.

There is a wealth of info on blackworms on the net - just do a google
search for blackworms, and you'll get lots of answers. (It's where I got
all of the above info.)