Let me offer my professional opinion on the matter: EWWWWWW!

No, seriously, I haven't heard of this, but it's hard to imagine anything like that standing up to a bathtub of bleach water (providing you aren't on a septic tank)

Fill up the tub with water, add a couple cups of bleach, mix it a little and then let it all go down the drain.

It will take several applications of a pesticide, followed by some drain cleaner to flush out the surface that harbors these little larvae.

Pour the pesticide in and tape over the drain to let it work for 24 hours. Mix it as you would to put in a sprayer but double the dose and mix enough to overfill the trap allowing some to exit into the drain pipe.

Here is a short video I made about drain worms in my shower because I realised that there was very little about them on the web. Hope it helps you beat these little nasties.

http://www.youtube.com/watch?v=px_f0JbwIrU&list=UU4bKk4PGekB_Wzqg5I1v8QA&index=1&feature=plcp
(see the link below)

In short, the Drain Worms hatch from the eggs laid by the Drain Fly in a layer of scum just above the water level in the pipe. So the worms you kill today will just be replaced by more hatchlings in the following days. The worms grow up to be Drain Flies and then they lay more eggs.

You've got three choices to break the life cycle: 1. Kill the flies, 2. Block the flies from reaching the scum by keeping the drain plugged or covered when not in use, 3. Open the grate so you can thoroughly clean the scum away.

They do not live in the grout. That just happens to be where most people see them. They travel from the drain out towards the grout as they make a hasty escape.

And by the way, they are not black. Check out the video for a closer look.
Cheers
Rusty

Here is a link that might be useful: Drain Worms and Drain Flies, how to get rid of them

They can appear when an unused drain trap dries out, such as a basement floor drain.

I suspect a quicker way to break the cycle would be to remove the strainer, scrub the pipe walls (above the trap) vigorously with a bottle brush, and then rinse with a bucket of water or two. Maybe add a bit of bleach to the water for that extra-clean feeling. That should move them along and put a kink in their breeding cycle.

I moved into a house with I thought same things. However I was,wrong. House had mold. They were parasites a,fungus got inside my body. Another name for it is Morgellons Disease some say soon will be an epidemic. I'm not saying that your situation is thex same yet please check thoroughly for i am si sick an weak and I left the home everything I owned over a year ago. CDC is covering something up. Look up Oklahoma University and parasites (worms ) . Have your place checked for mold. Nothing kills these things so make sure you do your own research. Pesticides will not touch them. Good luck.

Unfortunately I just had to deal with these larvae this weekend. We had a small leak in our shower door that allowed the water to sit under the bottom tread and this is where they made their home. Happened quick too, we saw the leak two weeks ago but I was hoping to wait for some time off to fix. Anyway I had wanted to kill these guys before pulling the door out and nothing seemed to work even bleach. But I did find something that did work...a few drops of tea tree oil kills them fast. I don't think I would count on this to break the life cycle though since I found more hiding as I took the door out and I am not sure if how long it stays active...but still nice to know how to kill them.