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A fishkeeper's guide to danios and devarios

Matt Clarke takes an in-depth look at the danionins, the subfamily which includes the Danio and Devario species, and covers a range of brand new fish.

A fishkeeper's guide to danios and devarios

Copyright © Practical Fishkeeping


I'm the type of geeky fishkeeper who tends to look in every tank in a shop to see if any of them contain fish I've never seen before in the flesh.

The past few years have been exciting for me as I've been spotting a much wider range of previously unseen aquarium fish from South Asia.

Stacks of exciting new fish have been imported from India, Myanmar and Vietnam which haven't been available before, and among these have been quite a few new species of danio.

Oddly, I think, danios don't seem to attract that much interest from fishkeepers. Most fishkeepers have kept the ubiquitous Zebra danio at some point, but few realise that there are actually dozens of different ones available, many of which are very attractive indeed.

The danio group is quite diverse and includes both small and large species, all of which will fit in well in the average community tank.

They're also peaceful, good-looking, cheap, and best of all, dead easy to keep. So, although some of them are so new that scientists haven't yet pinned
names on them, you shouldn't be too concerned about trying them out if you're still a relative newcomer to fishkeeping. If you're an old hand, there are almost certainly fish here that you'll never have seen on sale before.

Danios or danionins?


The danios are tiny members of the carp family ranging in size from just 3cm/11/3" up to around 15cm/6". At the moment the danios are split into two main genera, Danio and Devario, but the group also includes some close relatives like Sundadanio, Danionella and Microrasbora.

Although all of them are collectively called danios in the hobby, this can make things confusing when you're trying to talk about only the members of the Danio genus. Since all of these fish are members of a minnow subfamily called the Danioninae, pedants (such as myself) think that it's wiser to call all of the fish in the group danionins (pronounced dan-ee-oh-nins), rather than danios.

All danionins are fast-swimming, midwater or surface-dwelling fish, and generally live in large groups of 20 or more in fast-flowing shallow rivers and streams, sometimes at quite high altitudes.

A few of them also get stranded in weedier pools, canals and lakes when the rivers they live within burst their banks and flood. The waters they're found in are often turbid, and in "jungly" spots, the water may be heavily shaded and therefore a bit cooler. Many are really more subtropical than tropical.

One think they definitely don't like is too much carbon dioxide. During a product trial of some CO2 units for PFK, I added a unit to my main danionin tank and while the fish looked OK, they weren't that active. Upon removing the unit, the fish suddenly became much more active and more colourful.

Almost without exception, danionins are peaceful fish and rarely show any aggression towards each other or other fish, so you don't need to worry about what you mix them with.

You may occasionally get a little bit of squabbling within a shoal, and there has been the odd report of fish chasing male Siamese fighters, but in the majority of cases, their behaviour is exemplary, and they never really cause any harm.

The smaller species will mix well in any community tank while the larger ones, such as many of the Devario and Danio dangila, do well alongside slightly larger fish, including peaceful cichlids. These fish are such quick swimmers that they're easily capable of moving out of the way of aggressive fish and rarely seem bothered, even when cichlids are breeding around them. Most
fish simply ignore them.

Danionins are really adaptable, which makes them a doddle to look after. They're found over a wide geographical area, so some are found in slightly acidic conditions, while others live in slightly more alkaline waters.

Most of them will be fine in unadjusted tapwater, even if it's fairly hard and alkaline, although they invariably do better and are more likely to produce bigger broods if the water is neutral or softer. And, since they're sometimes found quite high up in mountain streams and in the less balmy waters at the foothills, they often do well in cooler water, too. You may even get away with some of them in an unheated aquarium if your house has central heating on all the time.

If your tank doesn't look particularly lively, these could be just the thing to grab the attention of people in the room. The group of Devario I added to my largest tank livened it up, and you can't help but look at it now.

Like most danionins, mine spend the majority of their time confined to the upper levels of the tank and cavort in the flow of the power filters. Most danionins feed on insects and small aquatic invertebrates. In the aquarium, they're ravenous feeders and will gorge themselves on anything that you offer them, from flakes to small pellets and granules.

Since danionins live in groups, you really ought to keep a shoal of about six or more. They're placid and quite gregarious creatures, so it's fine to mix different types together. There's rarely any problem in keeping larger Devario alongside smaller Danio and Devario species.

However, do bear in mind that in some circumstances, exceptionally large specimens could look upon tiny 1-2cm long fish as lunch. Some Devario, such as pathirana, will feed on the fry of other fish. One natural characteristic they have sadly replicated in my own aquarium...

The Danio genus


Members of the genus Danio are predominantly small fish, ranging from about 3cm/11/3" in the stunning Glowlight danio, D. choprae, to about 6cm/21/4" in the Zebra danio, D. rerio. However, there's also one outcast in the group called the Moustached danio, D. dangila. This doesn't really fit in well with the other fish as it reaches a comparatively massive 15cm/6". It's one of many species which have started to turn up in larger numbers in recent months.

Many members of the genus Danio, until a few years ago, used to be called Brachydanio. However, this name is now considered a synonym, so the fish have been renamed. Virtually all of the Danio species are found in Myanmar (formerly Burma). But because they're found in river systems that span several countries, many of them are also found in Laos, India and Pakistan. The Pearl danio, D. albolineatus, is even found on the island of Sumatra, which was once connected to the mainland.

The Danio genus includes nine described species - Danio rerio, D. albolineatus, D. nigrofasciatus, D. choprae, D. dangila, D. feedgradei, D. kerri, D. kyathit and D. roseus.

There are also quite a few undescribed fish which probably fall into this genus, including D. sp. "Salaween"; D. sp. "Hikari Yellow" and D. sp. "Hikari Blue" [Update: Molecular studies have now shown that Hikari Yellow and Hikari Blue are males and females of the same species, and are distinct from D. kerri.], and the stunning Danio sp. "Myanmar" aka D. sp. "Burma" (probably a close relative of nigrofasciatus).

Very recently, a fish resembling a Zebra danio with bright red fins has arrived in the shops as D. sp. "Red Fin". Some reckon it's a new fish, others say it could be a relative or race of kyathit, a species which does appear to have a few different morphs, including spotted and striped forms.

[Update: Danio sp. "Megahalaya" also turned up in the early 2005. This species is actually Danio meghalayensis, a fish previously synonymised with D. dangila, but now considered valid again.]

There's much debate on these new danios, so some of these might be genuinely new species, while others might simply be geographical morphs of existing fish. They're tricky to identify, since many are quite variable in colour.

As you'd expect, with the genus containing an oddity like dangila, there are two main groups within the Danio genus: the dangila group, and another group containing two smaller subgroups known as the Barred danios and the Striped danios. It's possible that these may later be split into two subgenera.

The Devario genus


Although most fishkeepers are aware of two or three species that get sold under the Giant danio label, such as aequipinnatus and malabaricus, there are in fact dozens of described species in the genus Devario, compared to only about 10 species in the genus Danio.

Several of these get quite big, so they're normally collectively referred to as Giant danios. However, this isn't really particularly apt for the group since many of them have adult sizes that are smaller than many Danio species - horai, manipurensis, apopyris, acuticephala and apogon, for example, reach only 3-4cm.

Over 30 species have been described and are still valid, including aequipinnatus, malabaricus, regina, acrostomus, apopyris, acuticephala, manipurensis, horai, apogon, annandalei, chrysotaeniatus, devario, fangfangae, yuensis, naganensis, salmonata, browni, fraseri, leptos, mae-taengensis, laosensis, assamensis, pathirana, shanensis, suvatti, neilgherriensis, spinosus, suvatti, strigillifer, affinis, quangbinghensis, peninsulae and sondhii.

Unfortunately, telling the difference between a Devario and a Danio isn't something that's easy. Other than a few hidden osteological features, the only other things that separate Devario from Danio are the P-stripe, which extends onto the caudal fin, and their short maxillary barbels - but these two features alone aren't always enough for fishkeepers to distinguish them properly.

If you really want to know which species you're looking at, you'll need to look at the skull bones using a microscope, and become an expert in morphological systematics...

The same difficulties apply to the handful of species sold in the shops as 'Giant danios'. Several different fish are sold under the same name, and telling them apart is tricky, or impossible, because many of those sold may in fact have hybrid blood from similar species getting mixed up with brood stock on the farms at which they're produced.

Sometimes, the hybrid blood may have got into the strain a few generations down the line, so they appear only slightly different to the norm, rather than obvious hybrids between two species.

Fortunately, the sizes and requirements of the Giant species are much the same, so it's not really worth worrying about this, unless you really want pure-bred fish.

Some of the larger-farmed Devario around at the moment don't seem quite as hardy as they used to be, and they may succumb to bacterial infections if stressed from their journey from the Far East. Dropsy is common in Devario, while smaller Danio species tend to be susceptible to Neon tetra disease, Pleistophora.

Keep a close eye on new purchases and make sure the dealer has quarantined the fish for a week or two before you buy them, rather than risking adding them to your tank of healthy fish. However, once acclimatised, they're generally easy to keep and fairly hardy.

The fast swimming nature and larger size of some of the Devario means that they can be safely mixed with other, slightly larger fish, including smaller or medium-sized cichlids, providing they're not too aggressive.

My group of D. devario and D. pathirana get along fine with some Asian Etroplus canarensis and Bermin dwarf tilapia, even when the cichlids are spawning.

How to breed them


Until recently, only a few species of Danio were being kept in the aquarium, so there aren't many records of the more unusual varieties being bred. A few experts in the UK have published some reports with some of the newer ones.

Strood Aquarist Society has some excellent articles on breeding some of the more recently introduced danionins. However, since they're all close relatives, you should be able to breed most of these using similar techniques.

That said, few of the smaller Devario species have been widely kept before, so it's not possible to comment on how tricky (or not) they are to breed.

However, as a general rule, the Giant danios, such as aequipinnatus, are said to be harder to breed than the Danio species, but in fish terms they shouldn't be too challenging if you've bred egglayers before. My own Devario pathirana have been spawning every couple of weeks, so even these shouldn't be too hard.

To breed danionins, you'll need a larger tank, say 76 x 30 x 30cm/30" x 12" x 12", set up Rundle-style with a bare-bottom, heater and air-powered sponge filter. The water wants to be of neutral pH (about 6.9-7.3 should be fine) and not too hard (6-8°GH) or warm (about 25°C/77°F) is fine.

Place a mixture of floating and weighted spawning mops in the tank to give the fish something to aim at when they release the eggs. Add a male and a single female to the tank in the evening, and leave them to it. It's worth putting a glass cover on the tank, too, as the fish may accidentally launch themselves out of the tank and on to the floor in the heat of the moment.

Hopefully, if the fish are in good condition, they should have spawned by noon the next day.

One of the trickier aspects of the larger Devario species though, is that females don't fill up with eggs as much as smaller Danio species, so timing the removal of the female could be harder to judge.

As soon as you've spotted the eggs on the mops, take the parents out, otherwise they'll start to eat the eggs. Lots of Devario species feed on tiny fry in the wild and will think nothing of tucking into their own young. I've never raised Devario offspring yet, but John Rundle, who has, says the eggs hatch in 36 hours and need to be fed infusoria , then newly hatched brineshrimp.

Bizarrely, recent research by McCune and McClure has shown that danios with fewer stripes have smaller fry. Even though adult D. rerio are about the same size as kerri and albolineatus, their fry are much bigger at the larval stage.

If you're trying to breed your fish, only keep a single species in the tank, as many of them have been shown to hybridise - even those which look quite dissimilar, like kerri and nigrofasciatus.

Fish to look out for

Danio kyathit
Common name: Kyathit danio, Orange-finned zebra danio.
Scientific name: Danio kyathit.
Size: 4cm/11/2".
Origin: Myitkina, Myanmar.
Notes: This rare danio from Myitkina has only been known to science for a few years, but it is starting to become more common in the shops.

If all of the fish sold as kyathit are the same species, then this species has quite a variable pattern as both spotted and spot-striped forms exist. Some look like Zebra danios with orange fins; others look more like Leopard danios with paler orange fins. There's another species on sale as Danio sp. "Redfin", which looks very much like it may be a brighter red form of the striped kyathit, to me.

It usually has four or five rows of irregularly shaped stripes or spots running from the gill cover to the caudal peduncle, with two of the rows forming stripes that extend into the tail fin.
Price: About £2.50 each.


Common name: Pearl danio.
Scientific name: Danio albolineatus.
Size: About 6cm/2".
Origin: Myanmar, Laos and the island of Sumatra.

Notes: The pinky-blue iridescent colours of the Pearl danio can look great under the right lighting (Triton tubes or old-fashioned Gro-Lux can make them look very showy), but they're quite silvery when young and, therefore, easy to overlook.

Buy a group of six or more and keep them in a well-planted tank with a good current. Feed them colour flakes, bloodworm and Cyclops to heighten the pinky colours.
Price: £1-1.50.

Common name: Zebra danio.
Scientific name: Danio rerio.
Size: About 6cm/2" and quite stocky.
Origin: Very common and found in Myanmar, India, Nepal, Pakistan and Bangladesh.
Notes: This is the most common Danio, along with the Leopard danio. The Leopard, once called Danio frankei, is now considered to be simply a spotted aquarium strain of the Zebra, and does not occur in the wild. Females can get quite big and fat, and the slender fish you buy as babies will treble in size fairly soon.

A good species to breed, if you have a separate tank spare for a breeding project.
Price: £1-1.50.

Common name: Blue danio.
Scientific name: Danio kerri.
Size: Up to 5cm/2".
Origin: Phuket, Thailand.
Notes: Danio kerri is listed in most fish atlases, but is still relatively hard to track down in the shops. Like D. rerio and most of the other Danio species, it fills out a lot as it matures to become quite a robust and deep-bodied little fish. Females are plumper than males and tend to be more blue, while males have more yellow.
Price: £2.50.

Common name: Glowlight danio.
Scientific name: Danio choprae.
Size: 3cm/11/3".
Origin: Irrawaddy basin, Myanmar.
Notes: The silvery danio has orange bars on the upper and lower lobes of the tail, an orange stripe along the back, and a bright orange-pink stripe along the flank, plus a number of small vertical bars. It's a very pretty little fish and has only been available in the UK for a couple of years.
Some believe that it belongs in the Devario genus, and it's sometimes misidentified as juvenile Devario maetaengensis.
Price: £1-2.

Common name: Moustached danio.
Scientific name: Danio dangila.
Size: 15cm/6".
Origin: Myanmar, India, Bangladesh and Nepal.
Notes: At 15cm/6", this fish dwarfs many of the so-called Giant danios. It's a stocky fish and needs plenty of space, so don't consider this species unless you have a tank of at least 90cm/36". Despite the size, it's very placid and easy to keep, and develops an attractive pattern of silver-gold spots on the flanks and enormously-long barbels as it matures.
Price: About £2.

Common name: Hikari danio,
Scientific name: Danio sp. "Hikari Blue" and "Hikari Yellow".
Size: About 5cm/2", and quite stocky.
Origin: Myanmar.
Notes: I used to think that the Hikari danio was simply a morph of kerri, but recent molecular work has disproven that! Instead, they appear to be a closely related undescribed species. Some danio experts reckon that both "Hikari Blue" and "Hikari Yellow" could be the same species.

In kerri, males and females are different colours, so the "Hikari Blue" could be females and the
"Hikari Yellow" could be males. Pete Cottle of Strood AS has bred these, but reckons it's not possible when the two forms aren't kept together. [Update: Molecular studies have now proven that the two forms are, in fact, a single species related to kerri.]
Price: £2.50.

Common name: Rosy danio, Red danio, Burma danio, Red and Blue danio.
Scientific name: Danio roseus.
Size: Up to 4cm/11/2".
Origin: Found in the
Mekong system in Myanmar, Thailand and Laos.
Notes: This new danio, described in 2000, is one of my favourites and makes the similar-look Pearl danio look quite drab. I remember seeing this species over 10 years before it was described, and Czech suppliers were starting commercial production.

It's a stunning fish. Both sexes, but particularly males, can develop spectacular blue and red colour. You sometimes see them mistakenly labelled as Pearl danios. D. roseus are more slender and have more rays in the anal fin (15-17 vs 12-14 in albolineata) and have two pairs of longer barbels, whereas albolineata has a short pair and a long pair. They live in cool water, so don't keep them too hot. D. sp. "Salaween" may be identical, although there is some debate over this.
Price: £1-3.

Common name: Spotted danio.
Scientific name: Danio nigrofasciatus.
Size: 3-4cm/1.33"-2.5".
Origin: Northern Myanmar.
Notes: This small, delicate Danio is ideal if space is limited as it only reaches a few centimetres in length. The pattern really needs to be appreciated at close range, so it's ideal if you've got your aquarium next to your armchair or on your desk.
There are a couple of other danios with spots that resemble this species. These may be geographical variants, or quite possibly new species.
Price: £1.50-2.50.

Common name: Burma danio.
Scientific name: Danio sp. "Myanmar" or "Burma".
Size: 3cm/11/3".
Origin: Myanmar (formerly Burma).
Notes: This beautiful fish has a pattern of very large dark metallic blue spots on bronze flanks. It's very similar in appearance to the spotted form of Danio kyathit. However, I think it's probably more closely related to Danio nigrofasciatus and reaches a similarly small size. The spots on sp. "Myanmar" are very well defined and sometimes blur into lateral stripes around the caudal peduncle.

However, unlike spotted kyathit, the caudal fin itself lacks the distinctive pair of stripes which extend from these lateral markings. This stunning species of Danio is definitely one to look out for if you only have a little tank.
Price: £2 upwards.

Devario


Devario pathirana
Common name: Barred danio, Tiger danio.
Scientific name: Devario pathirana.
Size: 6-7cm/21/4"-21/2".
Origin: Sri Lanka.
Notes: After years of trying, I finally managed to get hold of a group of these stunning Devario. Mine have developed stunning colours, with a longitudinal yellow-orange stripe on metallic-blue flanks interspersed with a number
of wide, vertical shiny blue bars. They're endangered in their natural habitat, so the locals were, very wisely, only exporting small quantities of them as well as trying to breed them for the trade.

In the past few months, captive-bred fish have become commercially available, so hopefully this will become much more common. These are probably one of the best-looking danionins known.
Price: £5-20 each.

Common name: Bengal danio, Sind danio, Indian danio.
Scientific name: Devario devario.
Size: About 10cm/4".
Origin: Very widespread - India, Nepal, Pakistan, Bangladesh and Peshawar Lake in Afghanistan.
Notes: This colourful Devario gets quite a bit of blue, orange and yellow on its fins and body, making it one of the most attractive species around. My males often spar harmlessly with male pathirana and display stunning colouration in the process. At the front end of the flanks there is a series of irregular pale vertical squiggles on a metallic blue background, while on the rear end there's a darker blue lateral stripe extending through the caudal peduncle and on to the tail.
Price: £2-7.

Common name: Firebar danio.
Scientific name: Devario maetaengensis.
Size: 4-5cm/11/1.6"-2".
Origin: Thailand.
Notes: This lovely little Devario is a relative newcomer and is often misidentified as Danio choprae by importers, despite coming from a different country. Juveniles do look similar, so I can see where the confusion arises. The posterior lateral stripe on maetaengensis is dark, while on choprae it's pale and shiny orange-pink.

D. maetaengensis gets bigger and stockier than choprae when adult and has a series of tiny vertical bars running along the middle of the flank from above the anal fin to the operculum. D. shanensis is quite similar and has been imported to the UK.
Price: Around £2.

Common name: Malabar danio, Giant danio.
Scientific name: Devario malabaricus.
Size: Around 12-15cm/41/2"-6".
Origin: Myanmar, Sri Lanka, western India and possibly Thailand.
Notes: This is one of the most common Giant danios, but the fish sold here might be hybrids rather than thoroughbred fish. Shipments of these often contain more than one species as well as fish that look slightly different from the norm. However, they're still lovely fish and look great in a spacious planted tank. Like most larger danionins, these love a bit of movement in the water and develop great colour patterns
if you keep the water fresh.
Price: £1.50-3.

Common name: Giant danio.
Scientific name: Devario aequipinnatus.
Size: 15cm/6" at most, usually smaller.
Origin: India, Nepal and parts
of China.
Notes: D. aequipinnatus is the other Giant danio that turns up regularly in the shops, but like D. malabaricus, the quality of the fish on sale might not appeal to the purist. This is a big, active shoaling fish, so you need to give it plenty of space. A 90cm/36" tank is the minimum for a group of five or six.

These will often spawn, though the eggs are normally eaten by the parents during the courtship ritual, and are a good choice if you want to try breeding one of the larger species.
Price: £1.50-3.

Model organisms


The Zebra danio is a model organism in genetic studies - more is known about its biology and genetics than probably any other fish. Many of the genes in Zebra danios have remarkable similarities to those in the human genome, so studying it provides a quicker and easier way to find out more about the genetics of humans.

In 2004 alone, well over 740 papers were published on their biology, mainly on genetics and developmental biology. One well-publicised use of laboratory danios has been in GM technology. Transgenic Zebra danios have been produced in various labs which contain genes inserted from other organisms, such as corals and jellyfish, which cause them to glow under special lighting.

Contrary to popular belief, these GM fish are not sterile. We reported last year that one US-based reader had bred them, although patent laws prevent anyone other than the licensed patent holders from distributing the offspring. As yet, these aren't available in the UK.

Further info



Update

Since this article was published in March 2003, Pete Cottle (who has since become a regular contributor to Practical Fishkeeping) has set up a new website devoted to danionins. If you want up to date information on all of the species currently available in the UK, the site is well worth a visit. More at: www.danios.info


This article was first published in the March 2005 issue of Practical Fishkeeping magazine.



Matt Clarke (published online: 04.07.05) 4258 words, 937 hits


About the author: Matt Clarke

Matt Clarke

PFK's Website and Technical Editor is a former fish biologist and lifelong fishkeeper. He holds two diplomas, a degree and two higher degrees in fish taxonomy and biology, and loves unusual fish.

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