GloFish® are a patented and trademarked brand of genetically modified (GM) Zebra Danio (or Zebra Fish) with either bright red, green, blue, or orange fluorescent color. Although not originally developed for the ornamental fish trade, they are the first genetically modified animals to become publicly available. Fluorescent Zebra Danios were originally created to help detect pollutants in waterways.^[1]

Sexing[edit]

Unlike Zebra Danios, male and female GloFish are both virtually the same colour, and so they must be differentiated by body shape. Sexing is difficult with juvenile fish. Males have a streamlined shape. Adult females develop a "paunch" as they mature, identical to that displayed by female Zebra Danios. Females also have a brighter gold tone to their metallic stripes, but this is difficult to discern without direct comparison to male fish.

Breeding[edit]

Intentional breeding of GloFish is prohibited due to license restrictions.^[2] It is made more difficult by hyperbaric treatment of the young to render them sterile.

Tank compatibility[edit]

This is a peaceful fish and should be housed with other peaceful fish. They will chase one another and other fish, but rarely inflict injury. They should not be kept with slow-moving long-finned fish as they may be nipped or bothered by the fish's active nature.

Diet[edit]

Standard tropical flake food is sufficient for their staple food, and should be fed in small batches 2 - 3 times per day. GloFish will take food off the water surface, or pick it out of the water as it falls. Bloodworms are highly desired by GloFish, as are any other live or frozen foods. They will also take freeze-dried shrimp. Any food other than live or frozen foods should be crushed slightly, as GloFish are small, and too impatient to chew at large pieces. Feed them a variety for best health, always feeding the staple flakes first.

Feeding regime[edit]

Feed once or twice a day.

Environment specifics[edit]

This is identical to that of Zebra Danios. They are active swimmers that enjoy long planted tanks and a moderate current (as from a filter or powerhead). The tank should be covered with a hood to prevent the fish from possibly jumping out.

Despite the fact that GloFish are very attractive under blacklight, they should not be kept under blacklight all night. As with any other fish, the lights should be turned off at night to give them a period of darkness. Long-term exposure to any lights can be stressful for the fish.

Behaviour[edit]

No differences between GloFish and Zebra Danios have been observed, aside from their coloration. They are shoaling fish, which should be kept in groups of three or more; like Zebra Danios, they find security in numbers.

Identification[edit]

GloFish were developed from Zebra Danios and aside from their color, they are exactly the same. The first GloFish introduced to the market had the dark horizontal stripes of the standard Zebra Danio. However, today’s GloFish were bred from the golden zebrafish variety and do not have this dark horizontal striping. Accordingly, the fluorescent colors are much more pronounced than in the original line.

GloFish are fluorescent. Under natural sunlight, their colors are very bright and attractive. Under incandescent light, their colors are equally brilliant. Under a black (UV) light in a completely dark room, they appear to glow (they appear to glow faintly when under black light in a partially-lit room). Generally, the best lighting for both low-light and well-lit environments is actinic (blue wavelength) lighting. Blue light really brings out the fluorescence in the fish and is quite striking.

Legality[edit]

These fish are illegal to import or sell in many jurisdictions (such as the EU, Australia, Japan, and Canada) due to general restrictions against genetically modified animals. It has been reported that a few pet shop keepers are attempting to sell these GM fish in the UK; if caught the owners will find the fish confiscated and destroyed. The shop owners will also be fined and possibly given a prison sentence.

Genetically modified fish are illegal in California. Despite GloFish receiving an approval from the FDA for not being any kind of threat, the company was unsure if or when they will take the costly route to make them available in California. However, it was ultimately approved, and is now available in California.^[3]

The company that produces GloFish has posted a License Notice on their website. This notice outlines the restrictions on breeding or selling the fish. It also includes information on the intellectual property rights covering these fish.^[4]