Zebra Danio (Danio rerio): a lively fish for small aquariums

Are you looking for a fish that will bring vibrancy to your aquarium? If you have a small tank, the zebra danio (Danio rerio) could be the perfect choice. This small member of the carp family (Cyprinidae) is one of the most popular aquarium fish, thanks to its compact size, ease of care, hardiness (suitable even for beginner aquarists), and remarkable energy.

Natural habitat

In the wild, the zebra danio inhabits small rivers and streams in Pakistan, India, Nepal, and Bangladesh. It can also be found in still waters, irrigation canals, and rice paddies.

Appearance and behavior

The zebra danio (Danio rerio) typically grows to 4-5 cm in length and has an elongated body. Five shimmering blue stripes run from head to tail over a silvery or slightly golden background, with these stripes extending onto the caudal and anal fins. Females are generally larger and stockier than males, with more rounded bellies as they mature.

In addition to the classic striped variety, some danios have spots instead of stripes, known as leopard danios (Danio rerio var. frankei). For years, leopard danios were considered a separate species (Danio frankei), but a 1996 study by Haffter et al. revealed that they are a spontaneous mutation. Interestingly, this variety has also been observed in the wild (Spence et al. 2008). Aquarists may also come across long-finned forms of both the zebra and leopard danio varieties. Fluorescent danios, known as “glofish danios” are available commercially in a range of bright colors, but be aware that they are banned in the European Union.

Aquarium setup for zebra danio

Danios thrive in both community tanks and small single-species aquariums. However, it’s important to remember that they are a schooling species. For a group of 8-10 fish, an 80 cm aquarium with a capacity of about 100 liters is ideal. In a smaller tank, this active schooling species won’t have enough space, especially if you plan to keep other species as well.

When designing your aquarium, keep their high activity level in mind. Place plants toward the back and sides to leave ample open swimming space. Danios typically swim near the top of the tank and eagerly feed at the water’s surface, so avoid overcrowding the surface with floating plants.

Use coarse sand or fine gravel as substrate, and since danios benefit from a heavily planted tank, consider using a special substrate designed for plant growth or an under-gravel substrate. Decorative elements like pebbles, roots, or even bamboo shoots can be added – you’re only limited by your imagination.

Water parameters for zebra danio

Zebra danios are quite adaptable to different water conditions, so there’s no need for special water preparation. However, it’s important to maintain good water quality by using an efficient filter and regularly changing the water. Be sure to cover the tank, as danios are known to jump, which can be dangerous for them. If possible, position the aquarium so it receives some direct sunlight during the day – danios love to bask in the sun, and this can even encourage spawning.

Maintain the water temperature between 22-24°C, though some breeders recommend an even cooler range of 18-24°C, as danios tend to be more active in cooler water. If your home is warm, you may not need a heater. The water hardness should range between 5-20°dGH, and the pH level should be kept between 6.5 and 7.5.

Feeding zebra danio

In the aquarium, zebra danios are omnivores that will readily accept any food, as long as it’s small enough. In their natural habitat, they primarily feed on small invertebrates. While feeding danios is easy, it’s important to provide them with a varied diet. Multi-ingredient mini-granules like Tropical Supervit Mini Granulat and Tropical Nanovit Granulat, or mini-flakes like Tropical Supervit Mini Flakes, are excellent options.

In addition to these staple foods, you can also offer Tropical Red Mico Colour Sticks XXS, which are highly attractive to danios. These sticks resemble tiny bloodworm larvae and, when moved by water currents, mimic live prey.

Aleksandra Kwaśniak-Płacheta  (Ph.D.Eng)

Bibliography

Haffter, P., Odenthal, J., Mullins, M. et al. Mutations affecting pigmentation and shape of the adult zebrafish. Dev Gene Evol 206, 260–276 (1996). https://doi.org/10.1007/s004270050051

Spence, R., Gerlach, G., Lawrence, C. & Smith, C. (2007): The behaviour and ecology of the zebrafish, Danio rerio. Biological Reviews, 83 (1): 13–34.