I used a BBQ charcoal starter chimney
Problem is there about 12-14 square inches of copper a 1/4 inch thick to heat up enough to pull a 3" cap off a 3" tube. I'd need 3-4 torches like that to do it.
It's ok though, although I don't really like the extra expense of the couplers it does add another feature to the tank. A steam punk look is what I'm after and I think the couplers will add to that effect.