A longtime fishkeeper discusses how to care and keep the oft-underappreciated pearl danio, a hardy candidate for a freshwater community setup.
Danio albolineatus is a widely available species that is a great addition to most community aquariums. Thespecies is commonly called the pearl danio,which refers to the pearl-like sheen of the body. Healthy, in-condition specimens often demonstrate a variety of beautiful color schemes. The majority of specimens sport an iridescent purple or pink body, a yellow or neon-orange stripe running roughly 1/3 or more of the body length to the caudal fin, yellow or neon-orange eyes, hints of olive on the body, and subtle hints of yellow in the fins.
D. albolineatus is a highly underrated and often overlooked fish by many hobbyists, as it may not appear to be an eye-catching species in a local fish shop due to being housed in brightly lit living quarters with little or no structure. In addition, D. albolineatus typically carries a small price tag, so hobbyists often assume that it will maintain the same dull colors once they get it home. Luckily, there are a few easy things that hobbyists can do to bring out the true beauty of this community aquarium mainstay.
D. albolineatus is a widely distributed species in Asian hill streams. Because of its wide distribution and its variety of colors in the wild, some in the scientific community believe D. albolineatus will actually turn out to be a single species within a complex of multiple species that are closely related. Regardless, there will need to be further investigation and studies within the scientific community to support these claims. These notions do not significantly impact hobbyists maintaining D. albolineatus, as any variant seen in the aquarium trade will be a hardy aquarium resident.
Being a native of hill streams, the pearl danioappreciates generous water flow, which can be achieved by a large hang-on-the-back power filter or canister filter. Powerheads are also an adequate method to supplement water flow in addition to the chosen filter. My group of 12 D. albolineatus is maintained in a 29-gallon (110-liter) aquarium filtered by a hang-on-the-back power filter rated for a 60-gallon (227-liter) aquarium. This strong filter provides adequate water movement and oxygenation to simulate the fish’s natural habitat.
D. albolineatus thrives in aquarium temperatures in the range of 68–77° Fahrenheit (20–25°C). Temperatures above this range can be tolerated, but are not recommended for long-term success with pearl danios, because higher temperatures can cause their breathing to become labored and their activity level to decrease.
These danios looks best when maintained in an aquarium with a dark substrate, dark background, live plants, and driftwood. Black sand for substrate and a plain black aquarium background may seem like dreary choices to some, but the reality is that these darker colors enable D. albolineatus to feel more secure and truly show its potential.
When I worked at a local fish shop years ago, the two tanks that held pearl danios were bare other than heating and filtering equipment. One tank had light brown gravel, and the other had light blue gravel. In both of these tanks the danios were a pale whitish/cream color with hints of purple and pink; needless to say they were not visually impressive. I moved one of the groups to a planted display tank with a dark brown substrate and dark blue background, and within a matter of hours their coloration became much more vivid and customers took notice. It is also of note that the neon accents of D. albolineatus look particularly striking under actinic/moon lights that simulate twilight conditions.
The pearl danio is an adaptable and hardy fish. Being able to tolerate a wide pH range of 6.0–8.0 and a wide hardness range as well, this species will thrive as long as extremes are avoided.
As with most other danio species, D. albolineatus spends the majority of its time in the upper half of the aquarium near the water surface. This choice of stratum within the water column coincides directly with its feeding habit in nature, which happens to be eating small insects at the water surface. However, being the hardy species that it is, D. albolineatus will not hesitate to feed at mid-water or even off the substrate, depending on the type of food added to the aquarium.
Being highly active, the pearl daniohas seemingly endless energy and is always on the lookout for its next meal. As a word of caution, always close the lid to your aquarium after adding food, as D. albolineatus can easily leap from a tank when attacking floating food at the surface.
The pearl danio is an unfussy omnivore that will happily consume most any commercial aquarium food offered, but a balanced diet will of course improve its color and vigor. I rotate feedings among brine shrimp flakes, spirulina flakes, color-enhancing flakes, and a frozen brine shrimp/blood worm mix. Small live foods are not required to maintain D. albolineatus, but they may prove to be a catalyst to initiate spawning should the hobbyist wish to do so.
Typical adult length for the species is 2 inches (5 cm), with occasional specimens reaching 2.5 inches (6.4 cm). Being a naturally shoaling species, D. albolineatus does best when maintained in groups of five or more. Depending on aquarium size and stocking levels, the hobbyist should try to maintain the highest number possible. Individuals within large groups of pearl danios will constantly interact and chase one another; this is part of their natural social interactions, and injuries from these behaviors rarely occur. When kept in numbers fewer than five, the playful chasing seen in a large group may become stressful for the less dominant individuals. When kept singly, D. albolineatus may be slightly nervous and hover in the upper corners of the aquarium.
Due to their high activity levels and requirement to be kept in numbers, pearl danios should not be maintained in any aquarium less than what is referred to in the hobby as a standard 20-gallon (76-liter) long. The larger the aquarium the better, and based on my experiences D. albolineatus thrives in standard aquariums in the range of 29-75 gallons (110-284 liters).
Having a manageable adult size and being non-specific about water parameters, D. albolineatus can be maintained with a wide variety of tankmates. It is important to take into account the pearl danio’s robust nature and constant activity when choosing tankmates. Small, slow-moving tankmates that would be passive at feeding time should be avoided.
The list of potential tankmates is endless, but some species that I have had success maintaining with D. albolineatus are various medium-sized barbs (Puntius spp.), robust medium-sized tetras (Hyphessobrycon spp., Moenkhausia spp.), various loaches (Botia spp., Yasuhikotakia spp.), corydoras catfish (Corydoras spp.), small to medium-sized plecostomus (Panaque spp., Ancistrus spp.), and of course other similarly sized danios (Danio spp.). D. albolineatus can also be utilized as a dither fish for many types of smaller and less aggressive cichlids including kribensis (Pelvicachromis spp.), keyhole cichlids (Cleithracara maronii), and flag acaras (Laetacara curviceps).