Keep the fish in the quarantine tank for 2 weeks and watch for signs of disease. If the fish gets sick, you can medicate the quarantine tank without affecting the chemistry of the main tank's. If you are going to quarantine the fish, you should acclimate the fish to the quarantine tank's chemistry, not the main tank. In this case, be extra careful to select healthy fish at the store, and carefully monitor your new arrivals for the first few weeks in your tank for signs of stress and disease. You always risk infecting the other fish in your tank when skipping quarantine.
Fish food is somewhat delicate.
Exposing it to sunlight, leaving the lid off so that damp can come in, or buying a very large container that takes 8 months to use up all can sabotage the nutritional value of your fish's food. To many fishkeepers, flake food is like rice. It will do for most every meal, but a little something else now and again is important. Take it seriously. The reason most folks have fish is, we hope, to observe them.