Tanichthys sp. 'Vietnam'

Tanichthys: named for Chinese boy scout leader Tan Kan Fei, who first collected the type species, plus the Greek ἰχθύς (ichthus), meaning 'fish'.

Known only from the small province of Da Nang, central Vietnam.

Images of the habitat depict a small stream with clear water flowing over a substrate composed of variably-sized small rocks.

Aquatic plants appear to be absent though marginal grasses and other vegetation are well-developed.

Minimum base dimensions of 45 ∗ 30 cm18 ∗ 12 in or equivalent are required.

Choice of décor is not especially critical though it tends to show better colouration in a heavily-planted set-up with a dark substrate.

The addition of some floating plants, driftwood roots or branches, and leaf litter also seems to be appreciated and adds a more natural feel.

Filtration does not need to be particularly strong though it does seem to appreciate a degree of water movement and will also do well in a hill stream-type set-up.

Likely to be a micropredator feeding on small insects, worms, crustaceans, and other zooplankton in nature.

In the aquarium it's easily-fed but for the best condition and colours offer regular meals of small live and frozen foods such as bloodworm, Daphnia, and Artemia alongside good quality dried flakes and granules, at least some of which should include additional plant or algal content.

Very peaceful indeed and an ideal resident of the well-maintained community tank although it will not do well with much larger or more boisterous tankmates.

As it places no special demands in terms of water chemistry it can be combined with many of the most popular fish in the hobby including other small cyprinids as well as tetras, livebearers, dwarf cichlids, catfishes, and loaches.

In a stream-style tank it can be kept with the smaller species of Danio, Devario, and Garra as well as many loaches.

It's a schooling fish by nature and ideally a group comprising 10+ specimens should be purchased.

Maintaining such numbers will not only make individuals less nervous but result in a more effective, natural-looking display while males will also display their best colours as they compete with one other for female attention.

Young specimens can be tricky to sex accurately but mature females are usually rounder-bellied and often a little larger than males.

Males also tend to intensify in colour when in spawning condition or sparring with rivals, and may develop extended dorsal and anal fins with age.

Like many small cyprinids this species is an egg-scattering, continuous spawner that exhibits no parental care.

That is to say when the fish are in good condition they will spawn often and when a group is maintained alone in a densely-planted, mature aquarium or outdoor container small numbers of fry often start to appear without further intervention.

Should a more controlled approach be required a separate, smaller aquarium can be set up.

This should be 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 glass marbles.

Alternatively filling much of the tank with a fine-leaved plant such as Taxiphyllum spp. or spawning 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 and an air-powered sponge filter or air stone(s) 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, and spawning should take place the following morning.

An alternative is to spawn the fish in a group with half a dozen specimens of each sex being a good number, although a larger aquarium may be necessary.

In either situation the adults will probably eat the eggs given the chance and should be removed after 2-3 days maximum.

Eggs should hatch in 48-72 hours and once free-swimming the fry may initially require Paramecium or other microscopic food until large enough to accept Artemia nauplii and suchlike.

This fish was first collected in 2009 and limited numbers have been available in the aquarium trade.

It's sold under several names including T. sp. 'lemon' or 'yellow white cloud', and has also been misidentified as the congener T. thacbaensis, a valid species occurring much further north in Vietnam.

Among Tanichthys species the popular congener T. albonubes is noticeably larger than T. micagemmae or T. sp. 'Vietnam', exhibits an overall reddish-brown colouration in the body that is lacking in the other two and possesses a less broad dark, lateral stripe on the body, below the paler stripe.

In T. micagemmae the ventral and anal fins are reddish, whereas they are bright yellow in T. sp. 'Vietnam'.

Diagnostic characters for the genus include presence of cornified tubercules on the snout posterior to the premaxila in males, and confluent narial openings.

Less clear is the phylogenetic position of Tanichthys within the family Cyprinidae.

It has been considered closely related to the genera Danio or Rasbora but recent studies, notably that of Fang et al. (2009) have suggested it to be more analagous with Tinca tinca, the common tench, and the putative subfamily Acheilognathinae, better known as the bitterlings.

The results also suggested that T. micagemmae is the parent species of the group in evolutionary terms with T. albonubes its younger relative.