Fish recommendations for a 5 gallon tank

Goldfish:

Goldfish are low maintenance fish that can grow to be more then 10 inches long. (Depending on how big their environment is) In a 5 gallon tank, I suggest you house 1 goldfish, since they grow fairly large. You don't need a heater for goldfish, as they LOVE cool water! Rocks and a decoration are good, but maybe add a plastic plant or two. Goldfish eat standard goldfish flakes and you can also feed them lettuce or peas for a treat. (I never do this with my goldfish) In general, golfish are filthy, and a filter is a MUST! Goldfish are good for low maintenance, but I find them not-so colourful and fairly boring.

Guppies:

Guppies are extremely beautiful fish and they are bred for show. I breed guppies, and I get great joy out of the new life they bring to this world. Male guppies are MUCH prettier then females and also, you almost ALWAYS get a pregnant female when you buy one. So I suggest you get 2 or 3 males, out of personal experience. Guppies don't require a heater, but their tank must remain at room temperature. Maybe purchase a thermometer along with the guppies, so you can always keep tabs on the temp. Guppies can withstand 50-100 fahrenhiet and they are EXTREMELY hardy fish. Although I have learned that males are more hardy then females as well. Male guppies grow to be about half an inch long, and females are typically half an inch to 2 and a half inces long. They are normally 2-3 dollars each.

Hint: You should really buy plastic plant(s) for your tank!