a 40 gallon breeder tank is not necessarily a great home for a tortoise. It is restrictive as far as space is concerned, and I find that some tortoises just can't be in an enclosure with glass (my red-foot used to flip himself over several times a day when his enclosure had glass doors).
I do, however, use a 40 gallon breeder tank as a temporary (if 5 years is temporary) enclosure for one of my russian tortoises. It's a female I've been raising from an egg that has just reached 5.5" and has been raised in this aquarium (and has no trouble with the glass). She has been very successful in it so far, seeing as she is so large and over a pound, yet she is only 1 year and 9 months old.
It would likely be a good starter tank for a redfoot or other medium tortoise for the first couple of years, or for a mediteranean tortoise (like a russian, greek, or hermann) for several years.
However, I warn anyone against using the tank as the criteria for what animal to get, the obvious exception being space restrictions.
Just do a little research. There are a lot of good starter tortoises out there. Definitely go with a CB baby though, and not a WC adult if you can.