Up to eight guppies can be in a 10-gallon tank. As a general rule, a one-inch guppy requires one gallon of water to live comfortably. An adult male guppy will grow to be 1.5 inches long, and an adult female will grow to be around 2 inches long. Keep these numbers in mind when determining how many guppies to bring home.
Additionally, guppies prefer living in groups or schools, so you should keep several guppies in a tank so that they don’t get lonely. If you’re new to fishkeeping, try keeping three guppies in a 10-gallon tank and add more fish later when you’re comfortable.