A Rainbow Of Fish

No, this article isn’t about rainbowfishes, though we’ll be sure to include one somewhere in our discussion. Rather, today we’ll be highlighting all the beautiful colors of the rainbow that freshwater fishes come in, proving once and for all that they can be every bit as vibrant as their marine cousins. From the reddest of reds to the bluest of blues, these species have every bit of ROY G. BIV covered.

Red... Rosy Barb (Pethia conchonius)

Starting off, let's sing the praises of the lovely Rosy Barb. This species has been an aquarium mainstay for generations, and it’s not hard to see why. With its small size, hearty nature, and sumptuous colors, this is a species that stands out in any aquarium. Pethia conchonius (formerly known as Puntius conchonius and, before that, as Barbus conchonius) is a widespread species in parts of Pakistan, India, Nepal and Bangladesh, occurring in a variety of habitats, including ponds, lakes and mountainous streams. Aquarium specimens are, however, almost without exception captively bred. With such a diverse ecological background, it should come as no surprise that this fish is very accommodating in captivity, and this is an especially good choice for unheated systems. But there are many other fine red choices. Honorable mentions go to the Cardinal Tetra (Paracheirodon axelrodi), some of the red variants of Discus (Symphysodon), and, of course, the shiny red of the Irian Red Rainbowfish (Glossolepis incisus).

Orange… Goldfish (Carassius auratus)

How could we not choose such an iconic golden fish? But you might be surprised to learn that the Goldfish is not naturally so golden. Maybe this shouldn’t be such a shock, as a bright gold fish is going to have a hard time hiding itself in the wild, and so natural selection quickly removes them from the population. This happens in artificial populations as well. The Goldfish has been introduced all across the planet, as well-meaning aquarists release their unwanted pets into ecosystems where they really ought not be. It doesn’t take long before the lumpy golden creatures begin to take on the appearance of their wild brethren, becoming increasing brown and sleekly proportioned. It’s a wonder that this species is so malleable in the hands of aquaculturists. Orange is a surprisingly common color for freshwater fishes. Consider the Red Devil Cichlid (Amphilophus labiatus) and its close cousin, the Midas Cichlid (Amphilophus citrinellus). Or the Sunset Gourami (Trichogaster labiosa var.) or the aptly named Creamsicle Molly (Poecilia sphenops var.). We could do a whole list just on orange freshwater fishes…

Yellow… Yellow Labidochromis (Labidochromis caeruleus)

There is no fish yellower than the Yellow Labidochromis, but, interestingly enough, this species is mostly blue in the wild. In the northern portion of Africa’s Lake Malawi where this fish is native, most populations are a pale shade of periwinkle blue. It’s only in a small region between the rocky reefs known as Charo and Lion’s Cove that it takes on its cheery yellow appearance. This fish caused a sensation when it first became exported in the 1980’s but, owing to how incredibly simple it is to breed this species (even for home hobbyists), it quickly became a ubiquitous offering. On the other hand, the delightful blue morph is almost never seen outside of specialist cichlid breeders.

Green… Green Rasbora (Microrasbora kubotai)

You’d think there would be quite a few green fishes out there in the world, what with all the verdant aquatic foliage to hide amongst, but this is not so. For whatever reason, this is actually quite the rare color. Maybe Kermit was right when he sang about the challenges of greenness? You won’t find anything truly lush and saturated in this wavelength, but a few example are worthy of mention. The Green Fire Tetra (Aphyocharax rathbuni) is probably the most familiar. Mature specimens do take on a hint of green along their backs, but the red covering its lower portions kind of steal the show here and lend this fish its other common name, the Redflank Bloodfin Tetra. A better choice might be the Green Rasbora (Microrasbora kubotai), which really does look quite green. This is a perfect choice for smaller aquariums, particularly those that are heavily planted.

Blue… Electric Blue Cichlid (Sciaenochromis fryeri)

It’s hard not to choose a blue fish whose color is “Electric”, but there’s actually a few to select from. The “Electric Blue” variant of the Ram Cichlid (Mikrogeophagus ramirezi) is certainly a fine choice, with its soft shade of blue. And then there’s the equally magnificent “Electric Blue” morph of the Jack Dempsey Cichlid (Rocio octofasciata), which, despite its pugilistic nomenclature, is a fine choice for most moderately sized community aquariums. But our winner here comes from Lake Malawi. Sciaenochromis fryeri is as electric a fish as there is. Though the juveniles and females might not show it, the mature males absolutely sparkle like a living sapphire. Just be sure to keep this fish in a group, or you might not see these colors at their fullest.

Indigo & Violet… Purple Danio (Danio rerio)

Indigo isn’t a real enough color, so we’ll just go ahead and ignore it in favor of its more attractive chromatic neighbor, violet. Unfortunately, nature has been rather stingy with the purple-toned freshwater fishes, but science has stepped up in a big way here. Through the magic of genetic engineering, researchers have been able to take the fluorescent proteins found in corals and jellies and insert them into the genomes of other creatures. There are all sorts of useful biomedical applications for this technology, but, additionally, these fishes make for gorgeous pets. These transgenic fishes are a rainbow unto themselves, coming in astoundingly bright shades of pink, blue, orange, green, yellow, and, yes, purple (AKA violet). There is a Purple Danio and a Purple Tiger Barb and a Purple Skirt Tetra. We even have purple Rainbow Sharks now, to go along with Purple Angelfishes and Purple Convict Cichlids (though these last two are not yet available in the US). There is even a Taiwanese company that has begun to create multicolored fluorescent fish that possess a true rainbow of colors. But, pretty as these may be, nature did it first and did it best.