It usually takes few hrs, days, weeks, or even months for any new fish to adapt to their new environment. Once they're established with their new place, the fury and their true characteristics will follow soon after.
As with feeders, I recommend feeding them at least once in a blue moon to keep their natural instincts and FURY within. It shouldn't be a main dietery suppliment since they do carry all sorts of disease and known to cause difficiency. Stick with raw meats such as beefheart, chicken, smelt, prawns, shrimp, etc. Remember to remove fats or skins, and never cooked or seasoned.
Moved to Feeding and Nutrition.