Your fish is a Crenicichla sp. bellycrawler. This is a Columbian pike, one of the most frequently seen pikes for sale in the U.S. Even so, it is not formally described in the scientific literature, hence "bellycrawler" instead of a true species name. If your pike has the red sides and dorsal ocellus that you described, it is a female. These fish can be pugnacious. Although texts describe them as getting larger, I've really never seen a female larger than yours. They seem to be slow-growing, for pikes. The males will get larger than that, though.