This or one of the livebearers is almost certainly the most commonly bought "first fish" for the tropical tank. Hardy as anything, they are one of those fish that people joke about being so tough, you'd have to flush them to kill them.
Because of this, though, they are often used as "cycling fish", meaning that they are bought first to "break in" the tank, establishing bacteria in the filter. But this also means that they have to deal with the bad water quality in the initial stages of setup (when the filter is unable to handle the ammonia produced), and believe it or not, they can and do die from "new tank syndrome", just like any other fish.
Danios are extremely easy-care fish and tolerate a wide range of water conditions (to a point!).
There are excellent for beginners, and can live in a tank of 10 gallon size.
However, they are active swimmers that delight in chasing each other back and forth like squirrels, so sometimes they disturb very quiet or shy fish. They do occasionally chase other torpedo-shaped fish, not in a malicious way, but rather believing them to be fellow danio playmates. In the community tank, they are best kept with other active and bold fish, preferably in a long (rather than high) tank, so that they have room to swim and chase. They prefer the company of their own, in small groups of 3-4 or more. They are completely unpicky about food, and will snatch up just about anything made for fish consumption.
Danios are some of the most easy egglayers to breed (well, next to the convict cichlid, anyway). Marbles, a mesh net, java moss or spawning mops should cover the bottom of a shallow and long breeding tank. Set it up as you would any other tank, and introduce a male and female (they are tough to sex when not fully grown, but the female usually has a deeper and broader body as an adult, and the male slightly smaller and darker). If the water conditions are to their liking, they usually spawn around daybreak, in the early morning.
They are egg-scatterers and show no parental care, which is why the bottom material must be laid down (to let the eggs fall through and keep the parents from eating them). When the eggs hatch, the young are very tiny, and can be raised on miniscule live foods when they start swimming.
There are a few other species of danio, including the leopard danio (B. frankei) and giant danio (B. aequipinnatus) as well as hybrids between the species; all pretty much have the same easy requirements.