unknown worms

[regius34]

just recently, i have spotted worms in my tank. some are easily identified as bristleworms. but there are some that i cannot id. they are about 1/16 of an inch in diameter. they also have what looks like 3 or 4 antennae or tentacles on their heads. i would take pics but my camera doesn't take good enough pics to id any ideas

 

[fungia]

maybe round worms, nematodes? they are everywhere and usually very small.

 

[Hippocampus Whoresea]

Can you do a bit more in depth as to what they look like...color? shape? Dwell in sand or rock? Do they contract into themselves like rolling a sock? Are they anchored in one spot?