There be somethin in that sand

Hi,
I was doing some light maint on the 37 gal sea horse tank, and used my trusty turkey baster to stir it up a bit and there were 100's of these very tiny tubes burried in the sand, at first I thought it was fish pooo and then I realized it was some type of tiny little worm tube. Never saw the worms only their tubes.
The sand is extremly fine sugar sized sand very fine.
I hope they are a good thing.
They may be in the main tank and found their way to the 37 gal thru the return.
Is there a larval stage to brisstle worms, or is this another species.
I 'lld take a picture but I am at work and saw the some mins before I departed I usally check the skimmer for skim height and pumps are all running and the lights are on a timer.
Doug

I found this
Snails That Worm Their Way Into Tanks by Ronald L. Shimek, Ph.D. - Reefkeeping.com

))Vermetids seem well-designed to reproduce in aquaria. Unlike most mobile mesogastropods, they do not copulate. The males, however, produce packets of sperm called "spermatophores" which are transferred to the female's mucous nets by a pedal tentacle, expelling the spermatophore into the water and "hoping" she will catch it. This is not a forlorn hope; the animals’ gregarious nature often means that someone of the opposite gender is nearby. The females collect the spermatophores and store the sperm to fertilize their eggs. Embryos develop inside the female’s tube and are maintained there until they have passed through the larval stages and have metamorphosed into little juvenile snails. They then leave the female and crawl around briefly, usually for an hour or less, before they cement themselves to a substrate (Strathmann, 1987).

Typically, the tubes’ apertures extend upward, probably as an adaptation to facilitate spreading of the feeding web. As the animals grow, they tend to erode a hole through the side of the tube fastened to the substrate and grow a new extension out of it; as they do so, they seal off the old aperture with shell material. At the end of the new extension, they construct another slightly larger vertical extension with the aperture at its end (Keen, 1971).)

 

I think I've had those strings b4 then they went away....