Well. Logic says if you spread the weight around like maybe using plywood under tank not having individual contact points it should be fine. Like the guy laying on a bed of nails. One or a few he'll be pierced, many closely together and the weight is dispersed he just has a bunch of tiny impressions. But he doesn't weigh in close to 600+ pounds either. A tile guy I am not. But I do know tile laid correctly should never crack because the set will cover the complete tile back. That being on a solid foundation as stated above.
Raised? I don't care how much reinforcement you have. If I were a tile guy I wouldn't guarantee it either seeing that in few years from now when you move I need to come back and maybe fix it for free and maybe there is discoloration and now you want it all replaced?
That being said. If it were my house and I wanted a tank, I'd lay don't some plywood and install my tank.