Blue Danio (Danio kerri)
Blue Danios are a peaceful and hardy species that can adapt to various water conditions, making them suitable for the beginner aquarist. In addition, these Danios are friendly fish that won't disturb or hurt anything too large to be eaten. These Danios are relatively common in the aquarium trade, and you should be able to find them if you want them.
Blue Danios are shoaling fish in nature; therefore, you should keep them in groups of 8 or more individuals. Maintaining these Danios in decent numbers will not only make the fish less skittish but will also result in a far more effective, natural-looking display. At the same time, males will also display their best colours as they contend with one other for female attention.
Blue Danios have no particular demands when it comes to water chemistry; therefore, you can combine them with the most popular fish in the aquarium hobby. Tankmates could include other small Cyprinids, Tetras, Livebearers and Rainbowfish, as well as Loaches and Catfish.
The ideal aquarium setup for Blue Danios would be a heavily planted aquarium designed in such a way to mimic a flowing stream or river with a darker substrate, as they may appear paler in a sparsely decorated aquarium. Adding gravel, smooth stones or different sized rocks will also add to the effect. In addition, driftwood branches and roots, along with some aquatic plants, with hardy genera such as Anubias, Bolbitis or Microsorum, are ideal because they can be grown attached to the decor.
Blue Danios prefer clean well-oxygenated water; therefore, good filtration is essential. The aquarium needs to be set up in such a way that they have a current of water flowing from one end to the other against which these Danios will constantly swim. Filter outlets or additional powerheads will help provide flow; however, it would be best to avoid torrent-like conditions because these Danios usually occupy calmer stretches in nature.
You will need to have a tight-fitting lid on the aquarium as members of this genus are excellent jumpers and can fit through tiny gaps.
Blue Danios have slightly deep torpedo-shaped bodies that are either powdery-blue or yellowish-green, continuing into the caudal fin, depending on their location. These Danios also possess some pinkish-gold lateral stripes that extend from their opercle to their caudal peduncle.
It might be helpful to know that populations from different localities vary in body colouration; for example, fish from the northern end of the range tend to be more of a blue colour, while those from the south are typically more yellowish.
|Scientific Name||Danio kerri|
|Other Names||Kerr's Danio, Turquoise Danio|
|Aquarium Level||Middle - Top|
|Difficulty||Beginner - Intermediate|
|Best kept as||Groups 8+|
|Lifespan||3 - 5 years|
|PH||6.5 - 7.5|
|GH||8 - 12|
|TDS||36 - 215|
|72 - 78℉|
22.2 - 25.6℃
Photos of Blue Danios
Blue Danios are endemic to Koh Yao Noi island in the Phang Nga province in south-western Thailand. However, this species has later been recorded from other islands in the area, including Ko Lanta, Langkawi and Phuket, as well as mainland southern Thailand in the upper Malay Peninsula, including Krabi and Ranong provinces. They inhabit forest streams and small rivers characterised by very clear water with rocks, boulders and gravel as a substrate. Aquatic plants are usually absent, but submerged surfaces are often carpeted with a rich biofilm while the small amount of vegetation grows thickly.
Other Danios of interest
What to feed the Blue Danio
Blue Danios are not picky eaters in the aquarium and will accept most foods. However, you should use a good quality dried product such as flakes or granules as the staple diet, but you should supplement this with frequent meals of small live and frozen foods such as bloodworm, mosquito larvae, daphnia and brine shrimp. These Danios will also appreciate the occasional vegetable treat.
How to Sex the Blue Danio
It is relatively straightforward to distinguish the males from the female Blue Danios. Adult males are slightly smaller and slimmer than females and are more vibrantly coloured. In contrast, Sexually mature females are usually larger, more rounded in their abdomens and duller than males. The differences are apparent when the fish are in spawning conditions.
How to Breed the Blue Danio
Like many Cyprinids, Blue Danios are egg-scatterers who exhibit no parental care. When these fish are in good health, they will often spawn, and in a densely-planted, well-established aquarium, small numbers of fry may start to emerge without intervention. However, if you would like to increase the amount of fry, a slightly more controlled approach will be required.
You can still condition the adult group together, but a breeding tank should also be set up and half-filled with water. You should dimly light the breeding tank and cover the bottom with a wide enough grade mesh so eggs may fall through but small enough so that the adults cannot reach them. Plastic grass matting can also be used and works very well; alternatively, filling much of the tank with fine-leaved plants or java moss can also achieve good results.
The water should be relatively soft and slightly acidic to neutral, and you should set the temperature towards the higher end of the range. You can add a small air-powered filter initially, and you should position it so that the current is directed down the entire tank length or install a mature sponge-type filter.
Once the adult fish are well-conditioned and the females are noticeably full of eggs, you can introduce one or two pairs to the separate tank.
You can initiate spawning by feeding small amounts of live and frozen foods to the pairs and adding small amounts of cold water every few hours in such a way that the tank is gradually topped up. The couple should then spawn the following morning. The fastest and easiest way to tell if the female has spawned is to look at her to see if she is noticeably slimmer.
The adults will consume any eggs they find, so it is best to remove them after a couple of days, at which point you should switch the power filter for a sponge-type unit to avoid fry being sucked into the device.
The incubation period is temperature-dependent to an extent. Still, it usually takes between 24 and 36 hours for the eggs to hatch and then 3 to 4 days after that, the young will become free-swimming.
Initially, it would be best to feed the fry with Paramecium or dry food of sufficiently small grade. Then, once the fry becomes large enough to accept more significant foods, you can then introduce them to microworm and baby brine shrimp.