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Cardinal Minnows
 
The Cardinal Minnow, Tanichthys micagemmae, is a close relative of the White Cloud Mountain Minnow. So far the only natural population of this fish that has been discovered is in the Bến Hải river system of north central Vietnam. This river originates in the Annamite Mountains on the border between Laos and Vietnam and flows through the Quảng Trị and Quảng Binh provinces. The type specimens were collected at 17°07’24”N, 106°58’12”E, in the Quảng Binh province of Vietnam.
This fish was only officially discovered in 2001 but already has a variety of common names in English. There is a strong probability that it had been collected earlier than 2001 but misidentified as Tanichthys albonubes.
 
Length and Longevity
The Cardinal Minnow is a small fish and rarely gets above 2.5 cm (1inch) long; this is a little smaller than the White Cloud Mountain Minnow. It can live for at least 5 years.
 
Water Conditions
Tanichthys micagemmae is native to the tropics and will survive temperature extremes of between 17 and 34 degrees C (between 62 and 93 degrees F) but is more likely to be healthy at between 19 and 24 degrees C (between 66 and 75 degrees F).
The type specimens were collected in a stream with a sandy bottom as is not at all surprising for a stream going through sand dunes. According to Mr. Freyhof the water at the site of collection was not tested. This fish is sometimes found in fast flowing streams but it mostly stays near the edges in amongst plants where the water is not fast flowing. A well planted aquarium is recommended for this fish with at least part of the aquarium having almost still water.
Cardinal Minnows are not fussy about either pH or hardness and will happily tolerate a pH between 5.5 and 8, and a similarly wide range of hardness, but soft water is generally preferable for this species.

The White Cloud Mountain Minnow is intolerant of Copper so it is very likely that its near relatives are also easily killed by Copper in the water, and great care is suggested if Copper is used for treatments.
 
 
Feeding
The Cardinal Minnow is an easily fed omnivore. In the wild they would eat small crustaceans and insects as well as other tiny creatures in the water. This would be supplemented with algae and the micro-organisms that grow in association with algae and on the surface of plants.
In an aquarium, they readily feed on fine dried and frozen fish food. Supplementing this with some live food such as Daphnia and mosquito larvae is a good idea.
 
Companions
The Cardinal Minnow is a small and very peaceful fish. They are a schooling fish so a minimum of four is suggested. They will get along well with other small peaceful fish, including some of the smaller tetras and danios. Goldfish are not a suitable companion for Cardinal Minnows.
The Cardinal Minnow is compatible with all the other fish in its genus, Tanichthys, and will school with them as it they were the same species. In spawning they also react to each other without apparent discrimination. Reliable information about whether hybrids between the different species of this genus will result from these mixed spawnings and if so whether these hybrids are fertile is lacking.
 
Long Fins
Some male wild specimens of this fish have been observed with long fins. Long finned ones are sometimes available commercially, but currently there are less different colour and shape varieties than are available with the White Cloud.
 
Sexing
 
The males have longer fins and more red on the tail while the females are usually fatter with a reddish hue on the body. Males can grow to be slightly bigger than females. Males have tiny raised tubercles under the eyes during the breeding season and their dorsal and anal fins are slightly longer. During spawning, males are grey below the lateral stripe.
Most of the pictures on this page are of males, but the picture on the left of this section is a female.
 
Breeding
The Cardinal Minnow is an egg scatterer and there is no evidence of any parental care of the fry. This fish seems to lay small numbers of eggs very frequently in the wild and will do the same in an aquarium. Although this fish is a schooling fish, the actual spawning often seems to involve only one pair out of the school at a time. The parents can eat the eggs but they are not avid egg-eaters like many fish. They may also eat some of the fry, but once again they are not great fry eaters.
If you have a school of mixed sexes in a well planted aquarium and no or few other fish some babies will succeed in surviving. Babies produced in this semi-natural way will be fewer in number, but the ones that survive are likely to be the more vigorous ones.
 
Controlled Breeding
To get a larger number of fry a special breeding tank needs to be set up. For one or two pairs an aquarium of as small as 25 litres (6.6 US gallons) can be used, but for school spawning with six or more of each sex a 50 litre (13.2 US gallon) aquarium would be more appropriate.
To prevent too many of the eggs being eaten the bottom of the aquarium can be covered in marbles or gravel the size of small marbles. The same effect can be achieved with spawning mats or by filling much of the aquarium with fine leaved plants.
The breeding tank should be dimly lit. The ideal water for breeding this fish is soft and neutral to slightly acidic, with a temperature around 24 degrees C (75 degrees F).
The sexes should have been separated beforehand and conditioned well on rich foods like black worms, either live or freeze dried.
The tank should not have a filter with small intake area and a high intake rate of water, this would remove the eggs and the fry when they hatch. Instead an air operated sponge filter will provide both aeration and filtration with little risk to small fry.
The ideal position of the breeding tank in one where it gets the morning light. With reasonable luck the fish will spawn the morning after they are first introduced to the tank. Because some predation of eggs and fry is likely to occur the parents should be removed within 48 hours of being put in.
 
Raising the Fry
The eggs will normally hatch in 48 to 72 hours, and the fry be free swimming two days after hatching. The normal first food is the mixture of microscopic creatures known as infusoria. Cultured infusoria should contain a good percentage of paramecium. If the breeding tank was set up with a lot of fine leaved plants there will already be a good population of paramecium. Banana worms are another good first food, if you are able to get a culture of these tiny nematodes. Microworms are more commonly available; they are too big for newly hatched Cardinal Minnows, but are an excellent supplementary food once the babies have started to grow.
These live foods can be supplemented with the finest commercial fry foods, or even a suspension of dried hardboiled egg yolk. If any of these are used, extreme care needs to be taken to avoid overfeeding.
 
Relatives
The White Cloud Mountain Minnow, Tanichthys albonubes, was discovered on the White Cloud Mountain in Southern China by Tan Kan Fei, a Boy Scout leader and scientifically described in 1932. Until 2001 this was believed to be the only species in the genus. Tanichthys means ‘Tan’s fish’.
The Cardinal Minnow is closely related to the more common White Cloud Mountain Minnow. The specific name ‘micagemmae’ comes  from the Latin micare, meaning ‘sparkle’, and gemma, meaning ‘jewel’. Based on genetic testing the ancestral species of the Tanichthys genus is probably the Cardinal Minnow. To distinguish it from the White Cloud the Cardinal Minnow has a pale lateral line often with small dark spots. The two black and white lateral stripes in Cardinal Minnow are of roughly equal width. The black stripe is about 0.9-1.8 times as wide as the white stripe, while in the White Cloud Mountain Minnow it is 0.3-0.6 times as wide. The stripe is also lower down on Cardinal Minnow than in the White Cloud.
Another species of the genus has been collected from a small island in Da Nang in 2009 in Vietnam but not yet scientifically described and at present is sometimes referred to as ‘Tanichthys vietnam’. This species, assuming it is confirmed as a true species, has bright yellow ventral and anal fins rather than the red ones of both the Cardinal Minnow and the White Cloud Mountain Minnow. Tanichthys vietnam’. It has yellow on the lobes of its caudal (tail) fin. This has sometimes been sold as the ‘Yellow White Cloud’. It has also been referred to as ‘Tanichthys lemon’. This fish has frequently been confused with Tanichthys thacbaensis.
Tanichthys thacbaensis (Nguyen & Ngo, 2001) is a species in the same genus. It is called Loodevietnami tanikala in Estonian, but the common names used for it in English merely add to the confusion with ‘Tanichthys vietnam’. Tanichthys thacbaensis was collected further north in Vietnam. Below are three pictures of Tanichthys thacbaensis by Andrew Bogott.
   
 
Threatened?
The IUCN Red List of Threatened species has insufficient data to assess the risk ofTanichthys micagemmae becoming extinct, but commercial and anecdotal evidence points to the high likelihood of this species and its near relatives becoming extinct in the wild very soon.
As with its better known relative, Tanichthys albonubes, the main reason for its impending extinction is the encroachment of human civilization, and especially the waste that goes into the rivers with rapidly increasing numbers of humans. The particular part of the stream it was originally collected in had not been used for rice cultivation as much as most streams in Vietnam because it was flowing through coastal sand dunes, so the aquatic ecosystem may have been less disturbed.
The population of Vietnam has increased from 52.7 million in 1979 to 90.2 million in 2014. During the same period the country has become increasingly industrialised.  The combination of increased human population and increased industrialisation is putting increasing pressure on the habitats that wild creatures, including small fish, need to survive. It is widely predicted that the human population of the country will continue to increase before it starts to decline.
There is no record of whether or not some fish species were made extinct by the repeated wars in the country over the centuries, but it seems likely. The ones remaining are seriously threatened.
 
Names
The scientific name is Tanichthys micagemmae (Freyhof & Herder, 2001). There are no synonyms.
In English it has many names, including Vietnamese Cardinal Minnow, Vietnamese White Cloud Minnow, Vietnamese Minnow, Blue White Cloud, Royal White Cloud, Dwarf Cardinal, Vietnamese White Cloud, Sparkle-eye Minnow, Dwarf Vietnamese Cardinal, New White Cloud, Vietnamese Danio, The Other White Cloud and Micagemmae.
In Finnish it is juovakardinaalikala, literally ‘striped cardinal fish’, to distinguish it from the White Cloud Mountain Minnow which is called kardinaalikala literally ‘cardinal fish’.
In German it is called Vietnamesische Kardinalfisch.
In Estonian it is Sädeliin-tanikala.
 
Sources and Picture Credits
The three pictures ofTanichthys thacbaensis are by Andrewbogott (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons.