Aspire Triton, Changing the Glass tank tube.

Hi there i recently got my hand on a Triton sub tank, and i have also got a nice red glass tube to go with it, but i fail to see how this comes apart, there is only one part on the bottom of the tank (once you have removed the base with the coil atattched) is a ring with 2 lugs oppisite eachother, i have tried carefully to undo this but failed as worried i will break something! Any ideas? :D