What snails are on my rock?

[masterlucas]

http://imageshack.com/a/img547/2449/demg.jpg

They are very small, about 1-2mm in size and they do not move. Any ideas?

[mcgyvr]

not snails... tube worms.

[Sugar Magnolia]

Spirorbid worms. Harmless little filter feeders.

[reeferstace]

not snails... tube worms.

Yep, those are spirobid worms. They are harmless filter feeders. Their numbers will rise and fall dependent upon available nutrients in your water column. They are calciferous so they encrust on surfaces like your glass, overflows, powerheads, etc. I keep them scraped off the glass.
A vinegar soak will dissolve the tubes from powerheads or other equipment. Spirobids encrusting on rocks, I simply leave them alone.