There are different kinds of tropical fish food. And it is interesting to note that not one kind will satisfy all types of freshwater fish, so you have to be really careful when buying any type of tropical fish food. Start by familiarizing yourself with the kind of fish you keep in your aquarium. Read a lot and do your research. You can also ask your local fish store for advice.
Tropical fish food can be dried. Dried foods are either in flakes or pellets form. Compared to flakes, pellets usually sink faster and can cause pollution if not consumed. There are also frozen foods or freeze dried foods. They are less messy, float longer, and their nutritional value lasts longer than unattended live food. Live food includes fish like guppies, worms such as white worms and earth worms, insects, and invertebrates. Take note that there are some tropical fish that eat only live food.