Factsheet 17

Microdevario erythromicron (Annandale, 1918)

Both of us remember vividly how our Microdevario erythromicron arrived here in summer 2001. They were wild caught fish coming from Myanmar (or Burma, as the country was known before), and they were embarassingly thin. We were ambitious to keep them alive, and by feeding them with freshly hatched nauplia of Artemia salina, we managed to save almost all of the 20 fish we had received. When they had fully recovered, it was no problem to get them used to eat some small frozen foods like cyclops and dry flakes as well.

For the aquaria, we use our tap water as it comes: with about 10° dH and KH respectively and a pH slightly above 7. This is suitable for keeping all our fish, and M. erythromicron is no exception. As they appreciate plants, their tank should include at least some java moss where they can hide. They are shy fish, and it usually takes some patience for the aquarist until they leave their safe hiding places and can be watched. But then, they are a remarkable sight because they come one by one in a way which reminds a little bit of the humming bird’s flight, and if there is one fish species among all those we keep here that deserves the term “neat”, it’s definitely this one.

M. erythromicron is, as the name implies, a very small fish that rarely exceeds 2.5 cm. Originally known under the genus name Microrasbora, the species in 1999 was transferred to the genus Danio by Kottelat and Witte. Nevertheless Fang and Kullander write: “Danio erythromicron is excluded from both Danio (s. str.) and Devario. Its generic status is pending further study.”So as long as the eminent scientists do not make up their mind, we stick to the old genus name as does fishbase which informs moreover that the species is not endangered and that it is harmless. Reassigned to Devario 2011, Ed.

Its natural habitat is Lake Inlé in Myanmar’s Shan State. The shallow lake lies 900 metres above the sea level and covers a range of about 2,500 square kilometers. It is known not only for its diversity of fish – many of them, like M. erythromicron, endemic – but also for its floating gardens and its fishermen with their unique leg-rowing technique. The lake’s water is relatively cool and hard, and M. erythromicrion is said to tolerate a temperature of 21-25°C, a pH of 7-8, and a dH of 9-19° 3; fishbase even gives a maximum dH of 25°2. This makes M. erythromicron an excellent choice for an aquarium in regions with hard tap water for aquarists who do not want to use techniques to make it softer. The relatively low temperature makes it even easier to keep this fish which can live in a group of at least five individuals in a small aquarium, and that makes it an especially nice fish for beginners.

A tank like this is also very suitable for breeding. M. erythromicron is a continuous spawner which uses plants to stick its eggs to. In case the fry is to be collected, the java moss (or whatever is used) can be transferred into a small plastic tank with tap water where the eggs develop. A plant surrogate like a mop made of wool is also accepted by the fish and can be handled very easily. In any case, the medium containing the eggs should stand on a small plate which is removed as well because the spawn is not very sticky and otherwise a large amount could be lost during the transfer. The eggs are of about 1 mm in diameter, translucent and on day 3 at 22°C, they hatch with a size of 3 mm, lie on the ground and are remarkebly pigmented.

We transfer these larvae to our “cuvettes”. They are 30 cm high glass tanks situated close to a window which include about 10 litres of water, aeration, some java moss and a few snails for cleaning up. This system is suitable in the first weeks of life for rainbow fish, killis, and carps like M. erythromicron which have small larvae. They are first fed a powder consisting of different kinds of nutrients until they are big enough to eat freshly hatched nauplia of Artemia salina. For M. erythromicron, it takes almost one week until they can be found swimming and at least once more that time until they catch the fist nauplia. They are kept several weeks in a “cuvette” until they are transferrred to a normal aquarium where their diet is gradually changed to flake and frozen food.

In case a bigger tank is available and a mixture of species including M. erythromicron is desired, there are three other endemics from Lake Inlé we recommend: the biggest one with 6 cm is Inlecypris auropurpureus, a tireless swimmer in gold and blue for the upper region of the tank; Microrasbora rubescens, which is pastel blue and red and can be found in almost all regions of the aquarium; and Sawbwa respendens, the naked fish without scales but with a beautiful red nose (the males which also have red tips on their tail fin) which rivals M. erythromicron in shyness. All four species can be kept in a well planted tank under the same condition concerning water, temperature, and food. The biggest problem that could arise are temperatures above 25°C which are not well tolerated (especially by Inlecypris auropurpureus), but that should normally be of minor concern. In essence, M. erythromicron and colleagues are worth considering as an alternative to East African cichlids when it comes to plan a tank with hard water – and they have one important advantage: they are not only interesting but also fish to relax with.

   1. http://www.su.se/forskning/disputationer/spikblad/FangFangKullander.html

   2. http://www.fishbase.org/Summary/SpeciesSummary.cfm?id=24410   

   3. http://www.deh.gov.au/biodiversity/trade-use/publicnotices/archive/draft-report/fish.html#74

© Ilse Lass & Guido Hoener of Fischhaus Zepkow, 2004.