Worm

hello everyone, i have a problem.
for the first time, i have seen a worm of some sort in my shrimp tank. it is long (1.5 inch) black very skinny and fast. as soon as i saw it, it wriggled at extreme speed and buried itself into the sand.
has anyone come across long, black skinny worms before?
in the tank, i have probably 50 to 100 red cherry shrimp (from about a quarter inch upwards) and a dozen assassin snails and was wondering if there are any shrimp types or snail types that might eat shrimp. i know that i could put guppies in the tank but they would also eat the shrimp babies
Thank you
ivor.

thank you Hampalong, that is great news. i am in the middle of washing my filters in very hot water doh!  so far only done the built-in filter which i am going to dismantle anyway, but my big internal i will clean properly in tank water
i had already decided not to feed shrimp for at least a week apart from lolly sticks which the shrimps demolish very quickly.
thank you
ivor