Devario aequipinnatus
Giant Danio
Classification
Cyprinidae
Distribution
Described from Assam state in northeastern India but since reported from a vast area including much of northern India, Nepal, Bangladesh, Myanmar and northern Thailand. Historical occurrences in southern India appear to be a result of misidentification (Pramod et al., 2010).
Habitat
At a tributary of the Pasuni River, Ganges drainage, Uttar Pradesh state, India the substrate was composed of clay, silt, cobbles and boulders and the water was flowing moderately. At another, high elevation, site in Meghalaya state, northeastern India the water was somewhat clear with a mixed gravel/cobble substrate and some overhanging marginal vegetation. At the latter sire other species included Danio meghalayensis and an unidentified species of Channa.
Maximum Standard Length
90 – 100 mm.
Aquarium SizeTop ↑
A tank base measuring at least 120 cm x 45 cm is suggested for long-term maintenance.
Maintenance
Not difficult to keep in a well-maintained set-up though we recommend aquascaping the tank to resemble a flowing stream/river with a substrate of variably-sized, water-worn rocks, sand, fine gravel and perhaps some small boulders. This can be further furnished with driftwood roots or branches, and while the majority of aquatic plants will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis or Anubias spp. can be grown attached to the décor should you wish.
Since it naturally occurs in pristine habitats it’s intolerant to accumulation of organic pollutants and requires more-or-less spotless water in order to thrive. Though torrent-like conditions are unnecessary it also does best if there is a high proportion of dissolved oxygen and decent water movement in the tank so a good-sized external filter/powerhead or two should be added, and ideally a rivertank manifold installed to provide unidirectional flow. Weekly water changes of 30-50% tank volume should be considered routine, and the tank must have a very tightly-fitting cover as all Devario spp. are accomplished jumpers.
Water Conditions
Temperature: Should tolerate higher temperatures provided its oxygen requirements are maintained but for general aquarium care a value within the range 73 – 79°F /23 – 26°C is recommended.
pH: 6.0 – 8.0
Hardness: 5 – 20°H
Diet
Known to prey chiefly on insects and their larvae in nature as with most danionins. In the aquarium it’s a largely unfussy feeder and will accept most foods. A good quality dried product can be used as the staple diet but this should be supplemented with regular meals of small live and frozen fare such as bloodworm, Daphnia, Artemia, etc. for the best colouration and conditioning.
Behaviour and CompatibilityTop ↑
Not an aggressive fish but can upset very slow-moving/shyer tankmates with its constant activity and quite vigorous feeding behaviour. It’s therefore only appropriate for larger tanks containing robust, similarly-sized tankmates. There are plenty of suitable choices including many cyprinids, loaches, cichlids, catfish and characins although as always when selecting a compatible community of fish proper research is essential.
It’s a schooling species by nature and ideally should be kept in a group of at least 8-10 specimens. Maintaining it in decent numbers will not only make the fish less prone to bouts of skittishness but will result in a more effective, natural looking display. Any aggressiveness will normally also be contained as the fish concentrate on maintaining their hierarchical position within the group.
Sexual Dimorphism
Sexually mature females should be rounder-bellied, less colourful and a little larger than males.
Reproduction
Like most small cyprinids Devario spp. are egg-scattering free spawners exhibiting no parental care. When in good condition they will spawn often and in a densely-planted, mature aquarium it’s possible that small numbers of fry may start to appear without intervention.
However if you want to maximise yield a more controlled approach is required. The adult group can still be conditioned together but a smaller tank with a base measuring around 45cm x 30cm tank should also be set up and filled with mature water. This should be very dimly lit and the base covered with some kind of mesh of a large enough grade so that the eggs can fall through but small enough so that the adults cannot reach them. The widely available plastic ‘grass’-type matting can also be used and works well as does a layer of marbles. Alternatively filling much of the tank with a fine-leaved plant such as Taxiphyllum spp. or wool mops can also return decent results. The water itself should be of slightly acidic to neutral pH with a temperature towards the upper end of the range suggested above. An air-powered sponge filter or air stone(s) should also be included to provide oxygenation and water movement.
When the adults are well-conditioned and the females appear gravid one or two pairs should then be introduced. If ready spawning usually taking place within 24 hours, signified by the female appearing noticeably slimmer. After 48 hours the adults should be removed whether spawning has occurred or not. Incubation is temperature-dependant to an extent but typically lasts 24-36 hours with the young free-swimming a few days later. Initial food should be Paramecium or similar, introducing Artemia nauplii, microworm, powdered dry foods, etc. once the fry are large enough to accept them.
NotesTop ↑
In recent years it’s become commonplace to refer to the stripes on the body and fins of danionins as follows:
- P stripe: or “pigment stripe” is the central, dark, lateral stripe on the body which extends into the caudal fin in some species. Stripes above it are numbered P+1, P+2, etc. and those beneath P-1, P-2, P-3.
- A stripe: the central stripe on the anal fin; the proximal stripe (above it) is A+1 and the distal stripe (beneath) A-1.
- D stripe: The submarginal dorsal fin stripe.
Following Fang (2003) [I]Devario spp. are characterised by: possession of a P stripe extending onto the median caudal fin rays; a short maxillary barbel (absent in some species); absence of the A stripe (a less distinct, relatively wide stripe is present in some species e.g. D. acrostomus, D. annandalei, D. xyrops); a short, wide premaxillary process (cleft in the upper jaw) with a tiny apophysis (bony tubercule) touching the kinethmoid bone; infraorbital 5 not or slightly reduced.
The current genus name has only been in general use since 2003 prior to which members were considered to belong to the genus Danio. Older, molecular, phylogenies tended to agree that the latter represented a monophyletic group consisting of two major clades; the ‘Danio devario‘ group containing the larger, deeper-bodied species and the ‘D. rerio‘ clade comprising the smaller, slimmer fish. The now defunct genus name ‘Brachydanio‘ was often adopted for the smaller species and is seen in much of the older aquarium literature.
In 2003 Fang Fang conducted a more detailed study based on morphological characters which included members of other related genera, and the results suggested for the first time that Danio represented a polyphyletic grouping i.e. not all members derived from a single common ancestor. The larger species with short barbels were therefore reassigned to the genus Devario while the smaller fishes with relatively long barbels were retained in Danio (with the exception of the type species, D. dangila which grows to 80-90 mm SL).
These results have largely been supported by subsequent phylogenetic analyses (e.g. Mayden et al., 2007), although Devario has still undergone a little reshuffling, particularly following the publication of Fang et al. (2009). In that study the two species previously comprising the genus Inlecypris were brought into synonymy with Devario and three species formerly included in Microrasbora were moved into the new genus Microdevario due to possession of shared synapomorphies with Devario. Fang et al. also appeared to hypothesise the existence of a monophyletic clade consisting of the genera Devario, Chela, Laubuca, Microdevario and Microrasbora , results upheld in the more recent study by Tang et al. (2010). The genus Betadevario (Pramod et al., 2010) is also nested within this grouping and is sister to Devario and Microrasbora.
The latter also confirmed that within the family Cyprinidae this ‘Devario clade‘ is most closely-related to a ‘Danio clade‘ containing the genera Danio and Danionella plus an ‘Esomus clade‘ which groups Esomus alongside Paedocypris and Sundadanio. Closer relationships within Devario itself require further research, however.
