They both have different housing needs. Most firebellies are aquatic and Tigers are terrestrial. I would not house them together. I do not have a tiger, but i do have firebellies. I have found that when they spend alot of time outside of water they are usually sick, or the water is bad quality, but they enjoy the water over the land.
I have also read alot about tigers, I have been wanting one for a long time!! They like dirt bottoms, with little water.
I am sure other people will be able to help you more. Good luck