Glowlight Carplet (Horadandia atukorali)

When it comes to small schooling fishes, aquarists should be well-familiar with groups like tetras and danios and rasboras, but what, pray tell, is a carplet?

Common names are an inherently imprecise way to understand where a fish sits in the grander scheme of things, but, in this instance, this terminology is somewhat useful. The family Cyprinidae is the largest family of fishes, and includes all of the barbs and minnows and rasboras and danios, as well as the carps. So one might think that a carplet must be a close relative of the true carps… a miniature carp, right? Wrong.

There are two genera that go by this name, Amblypharyngodon and Horadandia, and they sit in an interesting position in the evolutionary history of this family. More specifically, it’s their relationship to the fishes known as rasboras and danios that is noteworthy here. These two sister lineages are highly diverse and occur widely across Asia. Each is recognized as its own tribe, the Rasborini and the Danionini, and we find the carplets as the earliest group to diverge among the rasboras. (A third genus, Rasboroides, also occurs here. Aquarists will recognize R. vaterifloris, the Fire Rasbora… which should maybe called the Fire Carplet?)

That being said, neither of these genera look all that different from their cousins in the rasbora tribe. Amblypharyngodon includes a handful of species scattered across South and Southeast Asia, but none are prevalent in the aquarium trade. They’re small silvery fishes that range from small to relatively large in size, with the grandest of these topping out and around 8 inches.

The other carplets, Horadandia, are a common find throughout coastal portions of Sri Lanka and the southern states of India. There is some disagreement as to whether these two populations represent separate species or not, with the continental form sometimes referred to as H. brittani. Those from Sri Lanka are H. atukorali, and, in recent years, they have begun to enter the aquarium trade as an interesting nano fish.

The Glowlight Carplet, as it is known, only reaches around an inch in length, making it perfect for small tanks, especially planted ones. This fish has a light yellowish green color (chartreuse?) accentuated along the midline by a strip that “glows” a bit brighter. The effect is similar to many of the South American Hemigrammus tetras, like the Glowlight Tetra (H. erythrozonus), though the effect is a bit more subtle in the carplet. This makes Horadandia perfect for those aquarists looking to add a small, tightly schooling fish that won’t overwhelm an aquascape with loud colors. In a densely planted system, these little fish can blend in beautifully with their surroundings.

Aquarium care requires a warm, peaceful tank and a diet of frozen and dry foods. In the wild, their natural prey is presumed to consist mostly of cladocerans (daphnia or “water fleas”) and small insect larvae. Breeding is easily accomplished with well-conditioned specimens, and the females will scatter their eggs among dense foliage. Small live foods or commercial fry diets can be used on the young. Interestingly, this species is noted to be euryhaline, and, coming from coastal waters, it can tolerate low levels of salt, though this is certainly not necessary for its husbandry.