Pike (Northern Pike, Muskellunge, Pickerel - Esox sp.) don't generally do much but sit there until feeding. They're ambush predators. Sure they thrash smaller fish, but it's usually over in an instant. Bass (Micropterus sp.) are a little more likely to cruise around and pick at stuff. Keep the tank unheated and you could have them for several years in a 55 gallon tank. Check local laws regarding keeping game fish. If there is a size limit, legally you can't keep them under that size.