Based on their size and natural habits you would need a tank of at least 300 gallons for one. They are territorial and the size of tank for multiples would be truly massive. The tank would be a balance between open space and densely planted areas where they like to spend most of their time - this is how they hunt, they are ambushers of prey. The tank would need to include a chiller and they prefer slower moving water.
For food they would do fine on any larger fish pellet geared toward predators. - you would be able to mimic their natural diet with fish, crustaceans, frogs, and even birds or the occasional small rodent.