Dragon Head Guppy Male. These guppies come in various bright colors, including shades of violet, red, orange, purple, yellow, and blue. They are swiftly swimmers, the species of guppy are very active in the aquarium and chase each other all day. You can prevent the strong dragon fish from harassing the weak ones by providing enough hiding space. Three dragon guppies are recommended for a ten-gallon tank, though six to ten dragon fish can be kept in a twenty-gallon size tank.