Is this the sort of wood flooring that goes over a subflooring? It would seem that your floor joists would be more of an issue than anything else. I would assume that if your house is constructed in normal ways with joists on 16" centers, and they are sound, I can't imagine it being an issue whether the floor will hold a tank. Would you put a waterbed on it, or a big entertainment center with a 52" tv and all the accoutrements?
I, too, would be planning more on how to handle possible spilled water than worrying about the weight.