First, make sure you have some floating plants. Cardinals do not like overhead light, and the floating plants will immediately settle them faster.
Many of us do not feed fish the first day or two. The fish will be stressed from the move, and the new environment, and may or may not feed but it is one less thing to worry about.
From then on, I do not feed more than once a day, and I miss one or two days a week. Feed sparingly; it is better to think you might be underfeeding rather than overfeed. Prepared (dried) foods are very nutritious these days, depending upon the brand (I'll come back to these). One day a week you could also feed a "treat," such as frozen daphnia or frozen bloodworms. The latter should not be fed more often than once each week. I use the water change day (which should be the same day each week) as my "treat" day; never feed before the water change or any similar tank disturbance. I do the WC early in their day, an hour after the tank light is one; then, about two hours afterward, they get their weekly treat of the frozen foods.
For basic dried foods I use flake and tiny pellet. New Life Spectrum basic flake, Omega One Veggie Flake (their Kelp Flake is much the same, whichever); both these brands do not have "meal" in their foods but they are made from whole fish, shrimp, kelp, etc. For a pellet I have only recently tried Nutrafin's Bug Bites, which is basically dried insects, and the fish seem to really go for these.
I alternate the dried foods so the fish get something different each day from the previous. The above three foods cover three days, then repeat, with nothing the water change day and one other day.
