At my house we like our pets small, self-contained, and low maintenance. Beautiful, unusual, or weird is even better. But genetically modified? And only $5 each from the local pet store? How could I resist?

These gorgeous GloFish are zebrafish (called "zebra danios" in my local pet shop) with a little something extra. To be specific, jellyfish DNA injected into them when they were but wee eggs. According to the GloFish website:

The fluorescent color in our fish is produced by a fluorescent protein gene, which creates the beautiful fluorescence that can be seen when looking at the fish. The fluorescent protein genes occur naturally, and are derived from marine organisms. ... Every line of GloFish® fluorescent fish (i.e. Starfire Red®, Electric Green®, Sunburst Orange®, and Cosmic Blue™) starts with a single fish. The general process of developing fluorescent fish ... begins by adding a fluorescence gene to the fish before it hatches from its egg. Once the gene integrates into the genome (i.e., genetic code) of the embryo, the developing fish will be able to pass the fluorescence gene along to its offspring upon maturity. Because of this, the gene only needs to be added to one embryo; from that point forward, all subsequent fluorescent fish are the result of traditional breeding.

In ordinary light, GloFish exhibit bright DayGlo colors. But they really do their thing under ultraviolet light. Here's a video of our GloFish tank before and after we turn on the black light we keep around for scientific research:

Although we put this set-up together ourselves, you can buy special tanks with "GloFish optimized blue LEDs" built into the lids.

Now, GloFish are not rakunks, created by mad scientists intent on controlling the world. In fact, they were designed for good, not evil. The GloFish website explains how they are actually used in the fight against water pollution:

To achieve their goal of helping to fight water pollution, scientists are hoping to one day develop a 'switch' that will cause always-fluorescing zebrafish to selectively fluoresce in the presence of environmental toxins. A non-fluorescing fish will signal that the water is safe, while a fluorescing fish will signal trouble. To help further the research, a portion of the proceeds from sales of all GloFish® fluorescent fish goes directly to the lab where these fish were created.

Transgenic GloFish, like all zebra danios, are easy to raise, which makes them great for kids to try out. (The website contains lots of resources for kids and educators, too.) They can be fed crushed goldfish food (flake form), which makes them inexpensive to boot. I have kept a zebrafish or two in mini-aquariums for years at a time. The only caution is that some zebra danios are too territorial to play nicely with other fish and need to be kept in a separate tank. I bought my GloFish for around $5 each from Petsmart. They are not available in California.

To find out how to put together a quick-and-easy mini-aquarium of your own, just right for a GloFish or other tiny species, see my related post on GeekMom!