For future reference the dimensions of the tank are more important than the volume of the tank. I say this because 2 very different tanks can carry the same volume of water. For example while one could be rectangular and long, the other could be cylindrical and tall. For the most part a rectangular 250 should be fine.
Correct me if im wrong fellow MFKers
Silver Arowana: Minimum footprint should be 8ft x 2.5ft
Jardini: Minimum Footprint should be 6ft x 2.5-3ft