Danios are very similar to barbs but are much slimmer-bodied. They are Asian fishes and are found in large shoals in fast flowing waters. In the aquarium they prefer the upper layers of the water and may be seen cruising around all day. Most people buy just a couple, but with only two much of the beauty is lost as the fishes have no others to display to. They are peaceful, ideal community fishes.
They are insectivores and their upturned mouth is ideally suited to taking insects from the water surface. Fortunately for us, they are not fussy about food and will take flake and frozen foods without any hesitation. Bred by the thousand in commercial fish farms, albino and long-finned strains of Brachy-danio rerio (Zebra Danio) and Brachydanio albolineatus (Pearl Danio) have been developed. These strains are not quite as hardy as the wild type and require slightly higher temperatures. Both zebra and pearl danios are small fishes, the pearl not exceeding 6 cm (2 1/4 in) and the zebra 5 cm (2 in).
Danio aequipinnatus (Giant Danio) is larger, growing up to 10 cm (4 in), and a truly magnificent fish for the larger community aquarium. When they are well fed with plenty of live foods such as mosquito larvae and bloodworm, the blue/green background colour on the body is overlaid with golden yellow spots and bars.
Danios are prolific and very easy to breed. Males are slimmer and have more intense coloration than females, and often you can separate just a pair to do the job, but, as the male drives the female very hard, some people prefer to shoal spawn them. Set up your breeding aquarium with either marbles over the bottom or some Java moss, so that the fishes can scatter their eggs, but cannot eat them. No parental care is practised. As with the barbs, ensure that you have good supplies of small live foods, starting with infusoria and newly hatched brine shrimp, ready for the fry. Make sure the breeding tank is well covered as the fishes can be so active that they leap from the water.
A small fish that is often kept with danios, and has the same maintenance and feeding requirements, is Tanichthys albonubes (White Cloud Mountain Minnow), which is found in streams in the White Cloud Mountains of China. A most accommodating little fish, it can be kept in cool conditions, (as low as 16°C/60°F), and some people keep them outside in pools during the summer. Fishes that have been kept outside have more colour than those kept in aquaria, and this may be due to the abundance of natural foods, from insect larvae to algae.
Tanichthys albonubes breeds in the same way as the danios but ignores its eggs, so, left mostly to their own devices in a well-planted species aquarium or pool, they will multiply rapidly. The white cloud mountain minnow is probably one of the best egg-laying fishes a novice could try.