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Spawning the Blue harlequin rasbora.

Sometimes a change is required to keep your interest in aquatics fresh and to keep you enthusiastic. It was such as change that introduced me to spawning the harlequin rasbora for the first time. I am fairly well known as a cichlid keeper and am affiliated to two cichlid groups in the UK, being a committee member of the BCA and a active member of the NWCG, however I do keep plenty of other fish and as with all my fish I try to breed whatever I own. I have been very successful over the years with a long list of species bred.

Looking around my full fish room one Thursday afternoon, I decided that I needed a few fresh challenges to test my wits and provide a bit of fun, I jumped in the car and travelled to my local garden centre, this fish shop was never going to provide a rare fish to breed but I didn’t want or need that, I simply set a challenge to pick three species of fish that I had never spawned before which could not be a tetra, cichlid or corydoras (the three groups of fish I've bred the most of!) I was not fussed about difficulty or rarity, I simply wanted three fish that would challenge me in different ways. Looking around I picked out two pairs of Iriatherina werneri, the threadfin rainbow fish, a large pair of Puntius conchonius the rosy barb and finally amongst a batch of imported Harlequin rasboras I noticed a small group of the ‘blue’ color morph, a rarer find indeed!! I asked the assistant to bag all the blue fish and I came home with 9 in my bag.


The beautiful 'blue' colour morph of the Harlequin rasbora

Ive known all about Trigonostigma heteromorpha for many years, to me it was always classed as one of the ‘difficult’ fish to spawn and raise, I collect old fish books and magazines and going all the way back to the late 50’s and early 60’s there are reports of how fussy the harlequin is to spawn, in the initial stages of the hobby reports suggest that breeders in certain parts of Germany had no problem spawning this fish while others struggled to raise one or two fry! Tests of the local water reported it to be unusually soft and pretty acidic, perfect for these fish! The hobbyists who could not reproduce this water struggled in there efforts.

Trigonostigma heteromorpha is a very beautiful shoaling cyprinid found naturally in Southern Asia including Thailand, Singapore, Borneo and Sumatra, the fish inhabits warm, soft and acidic waters and is regularly found in peat swamps. Unfortunately man is encroaching on these pristine natural habitats and wild fish are a rare sight in the hobby, almost all aquarium stocks are raised in commercial fish farms, once there, humans have a natural reaction to try to improve nature and these fish are no exception, this has led to several colour forms of this popular and inexpensive fish, the most recent being the ‘Blue’ morph.

I considered myself to be pretty lucky to find these few fish and wanted to spawn them straight away, they were large fish with females obviously in good condition and egg bound, on my return I acclimatised the fish to my water (shop water was PH7.8, TDS 1200, my water was PH6.5, TDS 64ppm) and straight away setup two spawning tanks of 16x8x8, in these tanks I placed a silk artificial plant which I already had in use for the breeding of Nannostomus eques, and a plastic mesh as although I knew that the fish spawned under the leaf I did not know if they would eat any eggs that fell from the leaf! As it turns out the fallen eggs are slightly adhesive and stuck to the mesh instead of falling through, the mesh was discontinued for future experiments! Water was set to Ph 5.5 by using minute drops of Phosphoric acid and left to settle for a few hours, 6 hours later I picked out two pairs and placed them in the new tanks before switching of the fishroom lights and going to bed. Next morning both pairs were sat under the plant leaves doing nothing, one pair remained like this all day long(later discovered that they were two females, out of 9 fish 8 were female and only one male!) the second pair became more active as the day passed and by lunch time the male was starting to drive the female, id read all about the spawning procedure and it was nice to see the male ‘riding’ atop of the female, this continued for a hour or so until eggs were noticed under the leaves and a few on the mesh that had fell off. I made a few notes and watched with interest until spawning was finished around 2 hours later.



The pair upside down depositing eggs and fertilising them on the plant leaf..

I removed the pair to a stock tank keeping them separate from the rest, I then removed the artificial plant to a 5litre plastic container that I start all my fry off in and broke the tanks down for different breeding projects, the eggs hatched within 24 hours, and 48 hours after purchasing the fish I had around 60-70 quite large fry clinging to the tank sides, a few days later they were free-swimming and infusoria was offered as a first food, several days later they were fed with and excepted newly hatched baby brine shrimp and continued to grow with no problems at all. They are fairly fast growing (for someone used to working with painfully slow growing Apistogramma!) within 2 months the first batch of fish were already over a inch in size and ready for sale!


Large adhesive eggs stick to the underside of the silk plant.

They begin to hatch within 24hrs.


In the meantime I have continued to breed this species and have tweaked and experimented with them. I only have one male, normally with several pairs I would setup several breeding tanks at the same time to increase the chances of success, until I raise enough youngsters to give me more males I am stuck with just the one pair, after securing several hundred fry I decided to see if the male would spawn with more than one female, I setup two identical tanks of these fish, the first containing a male/female pair and the second containing two ripe females, both tanks had identical water(PH5.5, TDS 65ppm) and the same artificial plant. The pair started to spawn in the early afternoon (in all my breeding experiments this has been the only time they have spawned!, the fish house roof is semi clear so they are effected by day light and natural variations, Morning light for example) the pair finished as usual after a couple of hours, instead of removing the pair to the stock tank I removed the male to the tank next door containing the two females, the female was removed to the stock tank, the plant and eggs were removed to a tub and a fresh female and plant installed into the first spawning tank. Within the 20 minutes or so that this took, the male was now chasing both females in the second tank, both females were observed making dry runs under the leaves(no eggs produced) and eventually the male did spawn with both females in this second tank! This was now new territory for me and quite exciting, once finished, the male was now removed back to the first tank with yet another ripe female, his forth conquest of the (long) afternoon! Within half an hour the male had persuaded the female to spawn and in this forth attempt another spawning was performed, it was now a quite amazing feat that I had never witnessed before or had heard about from any other cyprinid breeder. Once finished, the stallion male! was removed to a quiet tank and given heavy feedings of white worm, brine shrimp and a granular food and the females removed to their own stock tanks and given the same treatment.

All plants that were used were put into the same container and noted which was which, I assumed that the later spawns may be effected by low fertility (a sensible idea due to the length and vigour of this males exertions!) this turned out to be not the case and all spawns were fertilised almost equally. From this spawning over 300 fry resulted, not a completely huge spawn given the amount of spawns but I have averaged below 100 eggs per female in almost every spawn to date, despite the females being medium sized and brimming with eggs. One other observation is that these fish can and will spawn on top of a leaf as well as directly underneath, 90% of the spawn is deposited under the leaf where the male joins the female side by side and fertilises the deposited sticky eggs, at other times the pair come together on top of the leaf and deposit the spawn on the upper section of the leaf, I first saw this when I was disappointed by a particularly small spawning under the plant leaves, upon further observations I noticed that most of that particular spawn was on the upper surface!!

Success.. A well fertilised spawn with most eggs hatching into baby fish!

Always a nice sight.. A well grown tank of your own bred fish :)

In all, ive really enjoyed working with these fish and am looking forward to continuing working with them for some time yet, I also spawned and raised both the Rosy barbs and Threadfin rainbows that I bought at the same time however neither captured my imagination or my heart the same as the Harlequin rasbora did, the Threadfins did offer some challenge in raising the fry but this was quickly mastered with the correct foods and both of those species have been and gone while the Blue harlequin has found a place in my fishroom and is a very enjoyable fish.

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