They’re just scavengers and eat anything in the bottom of your tank. I find they’re beneficial in for eating all the dead stuff, but one time I cleaned my tank and they all came up and started to latch on my angel fish’s fins… didn’t kill my fish tho. Could make a make shift trap for them then throw them out, but you can’t get rid of them indefinitely that way. Some fish eat them and that’s the best way to get rid of them
MichiganRefugee 
Planaria
They’re just scavengers and eat anything in the bottom of your tank. I find they’re beneficial in for eating all the dead stuff, but one time I cleaned my tank and they all came up and started to latch on my angel fish’s fins… didn’t kill my fish tho. Could make a make shift trap for them then throw them out, but you can’t get rid of them indefinitely that way. Some fish eat them and that’s the best way to get rid of them