Name: Trigonostigma heteromorpha
Origin: Thailand, Sumatra, Indonesia
The Harlequin Rasbora is a small colorful fish that can be kept in a shoal or by itself with other peaceful fish (examples-cherry barbs, neons, corys or platies). Water requirements are supposed to be acidic and soft, but I keep them in my hard alkaline water without a problem. If they are well acclimated they'll be fine. Males have a more rounded, clear bottom of the black triangle, while in females it is rather straight and blurry. They will swim in the upper to middle areas of the aquarium. They eat flakes, and small live food as well. Somewhat sensitive to ammonia and nitrite, but a very good fish for an established aquarium.
I've worked in a pet store for 3 years and we have had Rasboras - they are a very good community fish, very active and colorful. They tend to swim in the mid to upper sections of the tank. They are also a good starter fish for people just getting going.
I think that the Rasbora hetamorpha is a wonderful addition to most community tanks. They are best kept in groups of 4 or greater. Due to their small size they are a great way to add color without adding a large amount of size. They prefer a pH of 6.4-7.0 with a general hardness that is 30ppm or less (soft). I keep a group of 4 in a heavily planted aquarium. I love watching them swim amongst the leaves.
If anyone has ever kept the Harlequin Rasbora, they will know how beautiful this little fish really is, especially when kept as a good sized shoal in a well planted aquarium. It's red/purple/bue hues stand out very well under gro lux lighting, and photographs rarely if ever do the species any justice. There are at least two other species of Harlequin Rasboras - R. hengeli, and R. espei. These species are often over looked, as they do not seem to very photogenic, at least I have never seen a good photo of either fish. I currently own a group of R. hengeli, and I can say it is a spectacular fish, even when kept in hard alkaline water. Whereas the true Harlequin is mainly purple, R. hengeli is a brilliant red that defies description. It really has to be seen to be believed. I highly recommended R. hengeli to any Rasbora fanatics, or to anyone who wants something a little less "bread and butter" than the Harlequin.
Originally attracted by the nifty coloration of these fish, they were my first experience in keeping tropical fish. I had three in a tiny 8 liter aquarium (I'm a college student - it fit in my dormroom) along with a couple of pygmy catfish. They did great, despite the terrible water that this town has to offer (heavy metals, chlorine...) - I sometimes even neglected to condition the water. Now that I know better, I'm amazed they lived through this. I have since gotten a 110 liter tank, and moved my little t-bone/harlequin rasboras in there, and gotten them a few more friends (I now have 6 rasboras, along with angels, white clouds, catfish and bala sharks). They're all doing great, and I highly reccommend the harlequin rasbora to anyone considering some pretty, active little fish.
It's really sad when the Harlequin Rasboras lay eggs in my aquarium, because for one thing, I don't know where the eggs are. Also, the eggs are hatched at night, so when I wake up in the morning, most of the fry have already been eaten :(. I've only been able to save about five each time this happens. I've got some twisted Val's in my aquarium and I think that's where they lay their eggs, but I'm not sure. Harlequins usually lay eggs on the undersides of plants, so that's the best spot to look for their eggs.