Danios settling in

Danios are in

It has been almost a week since the Danios were added, they have settled in well and are relatively bold, but do not seem to appreciate when someone walks quickly across the room (as is expected). They certainly seem to enjoy the piece of wood, spending much of their time swimming through the holes in the base and around the stems, but do come right to the front of the glass when they notice me looking at them. The females are receiving plenty of attention from the males and one is looking considerably more plump now, so they may spawn soon.

The fish found the flow of the filter to be disturbing, so I have attempted to slow it down by wrapping filter wool around the rough sponge and placing more still between the sponge and the bio media. It seems to have helped slightly, but not enough, so I am still thinking about how to slow it down further. The stand building project has come to a bit of a stand still as I am quite lazy, but this has given me an incentive to get it going again because the external filter has a 300 lph rating compared to the 700 lph that came with the aquarium.

The fish are feeding well on frozen Daphnia and Artemia, with a supplement of high-protein granules and generic flakes. The 10 fish eat only tiny amounts, so even the smallest tub of fish food will last for years at this rate. Given that most fish food goes off in a matter of 1-6 months, it makes sense to separate it into smaller containers, freezing or chilling the majority of it until it is needed.

There have not really been any major signs of algae, I am still cleaning off mild signs of diatoms from the glass every couple of weeks, but that is it. Most of the plants are doing well, and I plan to split up one or two of the Cryptocoryne parva bunches into individual plants over the next week.

Danio margaritatus habitat

Since I wrote about Danio margaritatus, I have found the following information which is supplied by an exporter that has collected them from the wild:

First of all hobbyists puzzled that the fish was only discovered in micro habitat, one of the small pond at Hopong township, in Southern Shan State. Actually the fish is widely distributed in drainages of east side and west side of the Than Lwin River not only in Myanmar, but also in Thailand.

[…]

Distribution: East of Inle Lake, Southern Shan State, and North- eastern part of Thailand.

Habitats: Small pools with the depth 60- 90 cm, with some aquatic plants. The parameters of water of the pools are pH 7-7.8, conductivity 200-250 μS, and moderately hard. The temperature range 14-30 °C depending on the season.

Danio margaritatus

Danio margaritatus maleDanio margaritatus was first “found” for the aquarium trade in August 2006 and was quickly described by Roberts[1] as Celestichthys margaritatus, which is where “celestial pearl” comes from. Apparently there was quite a hurry to get the first paper out as a few groups were trying to describe the species at the same time. It was only a year later that the species was moved to the genus Danio by Conway[2].

This unusual little fish was originally found near the town of Hopong, in the same area as the similar Danio erythromicron, but unlike D. erythromicron, which comes from Inle Lake, D. margaritatus is found in small, shallow ponds with a high amount of vegetation. Over the next few years, more collection points were discovered, including in more areas around Hopong and as far as Thailand[3].

The fish became so popular due to its small size that in a matter of months, large parts of the habitat where it was originally found had apparently been destroyed, which triggered a blanket ban on export, but the Danios proved easy to breed, so captive bred specimens were almost immediately available. The fish appears to retain its beautiful colour when bred in captivity, while wild caught specimens are difficult to feed, so one should aim to only buy captive bred fish. It would be irresponsible to continue encouraging the destruction of a habitat through purchasing wild caught specimens. A couple of the more positive side effects of this species becoming so popular was the increased income of the local fishermen, who were paid 20 times more per fish when selling to the aquarium trade than when selling the fish locally for food, and an increase in availability of other dwarf species, such as Boraras, in the aquarium trade.

The recorded SL was 21.2 mm for a holotype male and 20.5 mm for a paratype female. It is quite possible that the species may grow slightly larger, especially since the specimens I bought are already around 20 mm, while the breeder said that they would grow another 30%, so would reach around 28.6 mm. Unfortunately, I was not able to see the parent fish to confirm this.

The temperature, as recorded by the closest weather station, which is approximately 400 metres higher above sea level and 30 km away, ranges from an everage low of 8 °C to an average high of 29 °C. From this, I would assume that the water temperature that the fish are found in would be within 15 to 25 °C, which is in line with what the breeder I bought them from told me: he said that the fish showed best colouration at 20-22 °C, losing most of its brilliant colouration at 25-26 °C. I had already assumed as much, which is why I set the aquarium heater to 20 °C as soon as the cycle was complete. This way, the fish should show best colouration for most of the year, only losing it in the summer, when air temperatures reach 30-35 °C.

Due to its natural habitat, this species is most likely best suited for small, shallow and well planted aquaria with low current. 60 × 30 × 30 cm aquarium seems to be ideal for the species as males may fight in smaller aquaria, but the fish “get lost” in larger aquaria. The majority of the plants found in the area were from the Hydrocharitaceae family, although the fish seem content with anything which provides a thick cover.

This species is compatible with most other small, peaceful aquarium fish which prefer plants and a slow current. Most of the Asian species I list as suitable for 60 litre aquariums should be comptible.

The fish’s diet appears to consist mainly of small invertebrates, although they readily take dry foods. For best colour, it is advised that the fish are fed a varied diet, including a large proportion of tiny live foods such as newly hatched Artemia and small water fleas. Due to the small stomach which is appropriate for the size of the fish, I would recommend that this species is fed small amounts of food often, for example, at least twice per day, although I expect that they would do well without food for a few days when kept in planted aquaria.


[1] Roberts, Tyson R. (2007), “The “celestial pearl Danio”, a new genus and species of colourful minute cyprinid fish from Myanmar”. Raffles Bulletin of Zoology 55(1): 131-140
[2] Conway, Kevin W., Chen, W.-J., Mayden, R. L. (2008), “The “Celestial pearl danio” is a miniature Danio (s.s) (Ostariophysi: Cyprinidae): evidence from morphology and molecules”. Zootaxa 1686: 1–28
[3] I do not have access to this reference: Hary, C. (2007), “Celestichthys margaritatus: Perlhuhnbärblinge gibt es nicht nur in Burma” (“Celestichthys margaritatus: pearl chicken Danioninae are not only in Burma”). Die Aquarien- und Terrarien-zeitschrift, 60: 6–9

Picking up the Danios

After a lot of searching online and in local fish shops, and one failed attempt to buy the fish from a breeder in the next big city (Potsdam) because the breeder sold them to someone else instead of waiting a day for a reply from me, I found a listing on eBay Kleinanzeigen (a classified listing website). While not as close as my usual fish shop, the fish were only an hour away by public transport, door to door, which was an improvement on 55 km that I was thinking that I would have to travel to find the not-so-local local breeder that I had found through a forum for local fish keepers.

This breeder was only at home from 19:00, so I made an appointment to see the fish and, after becoming slightly lost looking for the entrance to the apartment block, found myself walking into a small lounge with three aquaria. The breeder asked me to sit by one of them and observe the fish inside, while he told me about how he looks after the Danios. The Danios were bold, well coloured and a healthy shape, with the females being full of eggs. In short, these were by far the best D. margaritatus I had ever seen. After 10 minutes or so, the breeder showed me the foods he uses, which were newly hatched Artemia, frozen water fleas and high-protein dry foods. He explained that the fish hatched in July, and were power fed (fed small quantities of high protein foods often) so that they were now 70% of their adult size.

After I confirmed that I was very happy with the fish, and he made sure that I had the details for his frozen foods supplier, he started catching out the fish into a bucket, while I observed his other aquariums. He had a lovely nano aquarium, which was suspended from the wall, containing a beautiful pair of young Badis badis, a planted 2 metre aquarium with Pterophyllum scalare and Paracheirodon axelrodi, and a rack of breeding aquariums, one of which contained Hemiramphidae (halfbeaks).

Once the breeder had the 10 Danios in a bucket, I counted them and he proceeded to transfer them to the fish bag that I had brought along. Since the journey was short and it was 20:00 by this time (so quite cold, around 5-10 °C), the fish were packed with 90% water and 10% air. Under normal conditions, for example form an fish shop or for long journeys, the fish would be packed with 10-25% water and the rest air, as the oxygen that is in the bag is all that the fish will have for breathing for the whole journey. Once the fish were double bagged, I paid the breeder and headed home.

The trip home took slightly longer than expected as one of the trams was late, but because of the unusually high volume of water and a few layers of bags between fish and air, the water did not chill much. I arrived home at around 21:00 and proceeded to drip acclimatise the fish, which took 3 hours. Unfortunately, I forgot to test the water parameters for the record, but I expect that the breeder has roughly the same water as me given that he pointed out that he uses tap water. Once the bucket was full, I transferred the 7 males and 3 females to the aquarium, topped it up with dechlorinated tap water and headed off to sleep.