How to kill a vermitid sanil...

[Delphinus]

Man were you given off advice to leave it be. Following that advice myself my tank got so overrun with them at one point it was disgusting to look at because all you could see was those spider web things they put out.

All of the suggestions above will work. If busting off the tube, be sure to cut below the snail's body. They can retreat a fair way's back into the tube, so if you don't, all you're doing is giving it a haircut.

I've injected them with kalk to some degree of success.

Failing all other measures, take a wad of underwater epoxy and cover them.