The only way I can fully describe Trigonostigma heteromorpha, more often known as a Harlequin, is a little gem. A small shoal in a species tank is a sight to behold.
The keeping of T.heteromorpha is not difficult as they are very forgiving as to water conditions and seem quite at home and at ease with themselves in a normal community tank preferably swimming in a small shoal of at least six fish.
When shopping for T.heteromorpha you may be a little confused that what you see in the dealer's tanks doesn't always conform to the illustrations in your Baensch Aquarium Atlas. This is because the Asian and Eastern breeders (could be referred to as Bleeders) have messed them about genetically so we now have black, gold and albino varieties, and goodness knows what else is on the way?
Having said that, there are other near relatives to confuse you. Trigonostigma hengeli and Trigonostigma espei. Both these fish have a reduced size black wedge - the large well defined wedge being the true characteristic of the T.heteromorpha. When I look at a small shoal of fish that I really like in a dealer' s tank or perhaps at a friend ' s house, my imagination starts to run riot. I can imagine how spectacular it would look with say a hundred or more of the same fish swimming in a shoal in large planted aquaria. Wow!!! Quickly doing the sums it would be way out of the question on cost - but there is an alternative - you could try to breed them. This is why I tried my hand at breeding T.heteromorpha.
Now down to the serious stuff!! When looking for T.heteromorpha to breed, spare a reasonable amount of time going round the aquatic shops to find the best specimens possible. Never just buy the first fish you see. Six to eight good healthy fish would suffice.
When purchased, settle them into your community tank, taking the usual precautions, quarantine etc., feed them well and watch them closely. This is important as you want to be able to determine the sexes. When you feel you have achieved all this it is time to separate males from females. They do say absence makes the heart grow fonder and it is definitely quite true when breeding fish. Continue to watch the fish. When the females mature with a nice rotund belly and the males are stretching their finnage almost to breaking point they are ready to breed.
When I bred them I used a 15"x15"x15" tank. A similar size would suffice but note they do like a good depth of water to spawn. I filled my breeding tank with soft acid water to within one inch of the top of the tank. I used rain water but adjusted R.O.water would do just as well. The general hardness was about 2Dh and the pH was 6.5. Combined with a temperature of about 78° Fahrenheit should meet your requirements. The breeding setup should have the addition of a washed peat substrate of about one inch plus in depth.
My fish house is space heated so there is no need for a heater stat but include one if needs be. Finally choose a nice tall and generously leafed Java fern weighted at the root end with a strip of lead. You should try to ensure that the Java fern is as clean as can be without killing the plant. Hold it under a running tap of slightly warm water and bathe the leaves gently with cotton wool. Hopefully you rid the plant of most foreign bodies such as the likes of planarian worms, small leeches and hydra etc. I suggest that you wait a day or two to let the tank settle. There is one important point I nearly forgot - it is a good idea for the light to be entering from the top of the tank. I use a 15 watt florescent tube.
Now to the fish. It would be a good idea to introduce the T.heteromorpha about an hour or so before lights out. Float the fish in jars to equalize the temperature and when ready, using a small net, catch them and release them trying hard not to introduce any water from the holding containers. The fish will quickly acclimatize to their new environment.
Next day don't expect a great spawning spectacular. T.heteromorpha are not spontaneous spawners, they will build up to it over several days with the males showing more and more interest in the females day by day.
Fishkeeping and breeding in particular is about observation. I found that the first indications to spawning being always early morning with increased activity in the shoal, the males robustly showing off to one another with the females breaking away and showing interest in certain Java fern leaves. The females adopt a motionless position on the top side of the leaf and in an upside down position on the underside. Occasionally a male will dart down to see what is going on, the female remaining static he swims away and joins the shoal. Amazingly the female remains static for some time as if waiting for him to return. She then gives up and swims away.
When the males are ready to spawn they dance around the females gently nudging them and then positioning themselves over the back of the female. Rubbing their belly on the females back just forward of the dorsal fin, they again break away. The female takes up her static position on the Java fern leaf, but this time the male joins her. The eggs are laid and the male arches his back to the female and the eggs are fertilised.
The female lays just one or two largish clear semi - adhesive eggs at a time and repeats the procedure for several hours. They usually finish spawning about midday, you then have to make a decision:-.
a) Take the breeders out of the tank and leave what eggs you have to hatch in the breeding tank.
b) Carefully remove the plant with the eggs on it to another tank for hatching.
If you choose the latter, you then have the best of both worlds because if you replace the Java fern with another the T. hetromorpha being in a spawning mode will repeat the whole procedure the next day and possibly the day after. When removing the Java fern you must remember that the eggs are semi - adhesive. What I do is use a plastic ice cream tub which I gently immerse into the water lifting the Java fern slowly over the container and letting it sink down horizontally. Some of the eggs will drop off but will be retained in the container. Next fill a small tank with water from the breeding tank and carefully immerse the contents of the ice cream tub allowing the Java fern to slowly slide into the hatching tank. You should be able to observe the eggs on the leaves and of the eggs which became unattached, add an air line with a slight stream of bubbles to gently agitate the water surface.
Not all of the eggs will hatch. The duff ones will quickly turn white; the fertile ones will hatch in 36 hours.
The newly hatched fry look like slivers of glass hanging to the plant and sides of the tank. The fry will take newly hatched brine shrimp at about five days. Once they are on brine shrimp treat as any other fry. Growth is quite rapid but spawning is not large. I usually hatch about 30 from one day ' s spawning but if the spawning mode continues for several days - as it should - you will finish up with a nice shoal.
This is certainly not a study in ichthyology, just a personal account of a very pleasurable experience.
© Colin Roberts 2006. This fact sheet may not be reproduced in any form without the permission of the author.