well, its a worm, and i found it after it rained on the sidewalk (i kno i prob shouldn't of put it in the tank but too late now) so i guessed it was an earthworm, and i put it back outside when i found it today, on afterthought i shoulda kept it, or atleast took a picture, oh well
i did some research on earthworms and they actually can live in water, the reason the come out in rain is that the water is not oxygenated enough, but i have a good air pump in my tank with heavily planted, so i know oxygen is never a prob in mine