I cleaned out my sisters 10 gal, i emptied out 60-75% of the water that was left in there (its never completly full) and i found these little worms when i stired up the gravel, i'll admit i was not completly in the ball with this tank only b/c its not totaly mine its susposed to be the "family" tank. what are the worms from and can they hurt the fish?, there about as thin as a paper staple, and maybe 1/4 an inch long, there white, and there only out when i stir the gravel, do i have to boil the gravel???? help