It's a B-I-T-C-H to remove but it can be done....start by getting a little WD40 down under the outer rubber seal.... It takes some force thats for sure, you will need to grab it with your fingers and pull straight out, once it starts to free up try a little more WD40 around the seal. If you have a new lip seal/gasket then as Chazz67 said you may be able to pry it out with a screw driver, using a flat pices of wood to protect the tank..... once again you think getting it out is fun wait till you put it back in
No worry though, it can be done patients is the key.....Take it from me once your in there it's cheap insurace to replace you filter and rubber hoses so you don't have to do this all over again 6 months down the road....
