Worm thing
 

I just looked at the underside of the tank with a flashlight. Yikes! There was a ?worm? in the substrate about 2" long. It didnt like the light. Any ideas what it might be? Didn't see any legs.

Too hard to tell from the description really... a common worm seen in home aquaria that need ID'd are called bristle worms... next time your looking, check for bristles on the ends of its body.. (just dont touch them! ) haha

No bristles, dark brown & shrinks up fast when hit with light. Will try for a pic later when it comes back out.

Oh okay.. err, I don't know the name of that worm. But I have them too... they just seem to eat detritius and other junk in the rocks and tank. All in all.. harmless.

Possibly a peanut worm. I understand they are harmless nocturnal creatures. That would fit with its reaction to the light.

do they kind of look like an elephants trunk?

That would be the peanut worm... doesn't move just eats detritus... a good thing