It is amazing how often new fish owners get caught buying the wrong tropical fish food. Normally it is not their own fault. They go buy some fish at the local supercenter and are sold the fish, a starter aquarium kit, and a can filled with tropical fish food flakes.
Before you buy any tropical fish food you must take a little time and consider the fish you are planning to buy. Not all tropical fish thrive on those easy to use flakes. Many of them turn up their nose and simply will not eat them.
Since you probably ventured into the supercenter to make your purchase, you may believe there are no other types of tropical fish food since it is the only thing you see on their shelf. There are also freeze-dried foods, which can include tiny worms, like the bloodworm. They can include tiny freeze dried brine shrimp, and many other tiny critters fish love to eat.
Along with freeze-dried, your better pet stores will have frozen foods for your picky eaters. Frozen foods retain the normal moisture content and closely mimic live food. Even then, not all tropical fish will eat flakes, freeze-dried, or even frozen tropical fish food. Some species of tropical fish will eat nothing but live food.
A great example is if you venture into the exotic and buy a piranha or a puffer fish. Both of these varieties of fish want nothing to do with floating food. They want to hunt down their prey and eat it. The archerfish is another great example, but instead of living shrimp, or other marine life, they want insects on top of the water. They use their water shooting skills to knock the insect senseless and then eat it.
The point, you must research the species of fish you plan to have in your tank and then buy the food to match it. Your other option is to decide you want the easy path. Go ahead and buy the tropical fish food flakes and then purchase only fish which are happily eating it. Great examples of fish happy with flakes are tetras, most cichlids, and even goldfish.
Even after you have matched your tropical fish food and species of fish the fun is just beginning. You will need to learn how to balance the quantity of food with the amount of fish in your tank. Most people recommend when using flakes to only put in enough food for the fish to completely eat within 2 to 3 minutes. It sounds like a minuscule amount of food, but if you overfeed you end up with dirty water, higher amounts of ammonia, and will feel you are constantly cleaning the tank.
Most tropical fish food only needs to be given once per day, but this is once again specific to each species. The best advice is to fill your tank with fish with similar dietary needs to simplify your feeding chores. You can fill a tank with beautiful variety, color, and activity while still keeping them all on one feeding schedule and type of tropical fish food. It just takes a little planning on your part.