There seems to be a definite trend in aquariums today, with most of the action being on the two extremes, the very large and the very small. The small aquariums, usually referred to as “nano tanks,” are extremely popular and there are many available from 1 to 6 gallons. Most of these come in packages with filtration and lighting, but without a heater. Not having a heater is not really a problem, since most of the fish that should be kept in these small tanks can do just fine at room temperature. After all, you are not going to keep discus in a 6 gallon tank.
From my way of thinking, there are two important aspects for selling nano tanks. 1) you must have a knock-out nano tank display set up in your fish store; and 2) you must provide the right fish for the nano tank setup. Having a display nano tank in the fish store is really simple, as they do not take up much space, are easy to maintain. Also, nothing helps sell like seeing an aquarium with fish in it. When it comes to stocking a nano tank with the proper fish, things get a little dicier. Often juveniles of some fish species are sold, with the idea that the hobbyist can remove them when they get larger (they won’t do this) or that the “fish only grow to the size of the container” (which is false).
Fortunately, there are lots of fish coming into the aquarium hobby today that are good for nano tanks. These are basically new rasboras and danios that have been found in the wild and are being bred commercially. Of these, the best fish for nano tanks is the celestial pearl danio (formerly known as the galaxy rasbora until ichthyologists figured out it was, in fact, a danio). Celestial pearl danios are very hardy, don’t care about temperature or feeding, and are at most only 1 inch at maturity. Keep them on a dark-colored gravel with a few plants and their colors really come out. They are now being raised commercially, so the price has come down. The celestial pearl danios should definitely be the stars of the section of your fish room that features fish for nano tanks.