Once established, they are fairly tough, but they often will not take any prepared or frozen foods as juveniles. It's important to have a live food source--snails, live brine, live bloodworms--on hand when first purchased, and then wean them onto prepared foods.
I agree with DD, ltldrgon--the sharks are eventually going to fight. Most will get along as juveniles, but adults are very territorial and 72 is not big enough for the numbers you have. I would remove all but one. Even the algae eater will be attacked by the sharks, due to similar body shape. I originally had my rainbow shark in with my puffers. He was moved after about 8 months--the puffers started shredding his fins. Monitor the tank very closely, and be ready to remove fish.