Glofish are the first genetically-engineered pet fish to hit the aquarium trade. Previously, unscrupulous dealers could get these types of fluorescent colors only from a fish by injecting them with dyes, a controversial practice at best. However, Glofish have bright, DayGlo colors without any discomfort to the fish.
Despite their colors, Glofish still are zebra danios (Danio rerio), also known as zebrafish. They are smaller fish, under two inches. However, they prefer to live in groups and swim very actively, so they need a medium-size aquarium despite their small size. An aquarium with a capacity of at least 20 gallons will suffice. Glofish do better with longer tanks, since this gives them more horizontal swimming space.
Since Glofish ultimately are zebra danios with an extra gene, they have the same water requirements as their wildtype brethren. These fish are relatively undemanding, and can thrive across a range of water requirements. Their home waters range from 65 to 101.5 degrees Fahrenheit. However, their "ideal" conditions cover a smaller range of temperatures, between 65 to 77 degrees. Since Glofish require temperatures on the lower end of tropical, you may be able to keep them without a heater in most climates. They also can thrive across a wide pH range between 6.0 and 8.0.
Glofish have the perfect demeanor for a community-style aquarium. Despite their novel appearance, there's no reason they cannot share an aquarium with other small, peaceful aquarium fish. The biggest concern in selecting a tankmate is to avoid fish that can eat the Glofish. Glofish can share an aquarium easily with tetras, loaches and small catfish, like cory catfish.
In the wild, zebra danios live along riverbanks in densely vegetated areas. In captivity, you should replicate these conditions. Make sure their aquarium includes dense vegetation, so they feel safe. Plastic and silk aquarium plants work just as well as live plants, and require less work. However, you also should include open swimming areas for them. If you want to breed them, keep a layer of marbles, 1 to 2 inches deep, to protect the eggs from the parents. However, keep in mind it is illegal to sell the offspring, since these species are patented.