The Amazon River system in South America is home to a dazzling variety of small, colorful, schooling fish known as Tetras. They are justly popular aquarium fish with their glittering colors and synchronized schooling behavior. However, few fish keepers keep them properly and in sympathetic surroundings that shows them at their best. In this post, I’ll show you how to keep these beautiful little fish beautifully.
First, the origin of the common name; Tetra. When explorers brought back fish from the Amazon region in the teens, 20’s and 30’s, science lumped them all, big and small, into the Genus Tetragonopterus based on the number and shape of their teeth; which all Tetras have, from little Neon Tetras to the fearsome Piranha. That Genus is now almost totally vacated, and applies to only two fish I know of; T. argentus and T. chalceus, both ovoid, silvery Tetras.
The vast majority of Tetras available in the hobby do best in moderately soft, pH 6.8 water at 75 to 78 degrees, though nearly all are adaptable to a point. They are rarely as colorful in hard water and at high pH, and are more prone to disease in such conditions. What they like are well-planted tanks with driftwood and stones. They don’t like very bright tanks, so floating plants should be provided over the main viewing area so the light is filtered. I primarily use Amazon Frogbit (Limnobium laevigatum) for this purpose, though any floating species would do. Tetras look most attractive and colorful swimming through the shadows and light. Dark-colored substrates intensifies their colors.
Tetras are all long-lived, especially for little fish. You should expect at least five years with your charges, though with some species, you could enjoy them for more than 10 years.
One item that many overlook is that Tetras are very much schooling fish, thus for their continued health, one is obligated to keep them so. How many? In a well planted, established and filtered 20 gallon, 48 neon-sized Tetras easily. In a larger tank, say a 75 for example, it’s not at all difficult to keep 10 dozen.
Why? Because the neon-sized Tetras impinge so very little on water quality.
Feeding is another matter. Tetras have teeth, meaning their diet should contain meaty items primarily, with vegetative foods a smaller percentage. ALL of them do better and are more active, colorful and vivacious if fed live foods two or three times a week. Daphnia pulex is a favorite, though they do like wingless Dropsilia species fruit flies. The small Tetras can choke on things like white worms, so they should be cut into halves or thirds before feeding. A good pelleted food should be the staple, with vegetative foods, like Spirolina flakes, a couple times a week. Live food (if available and clean) as a substitute for a meal two or three times a week.
Feeding should be small meals given often, rather than one large meal a day, as Tetras are nibblers, not gorgers. As they are fast eaters, no more than they can finish in a minute three to five times a day.
So, give them the sympathetic surrounding of a soft, slightly acid well planted tank coupled with a good diet, and your Tetra tank will be the envy of all who view it.
Now some species
A little fish dropped a nuclear bomb on the aquarium world in 1933. Now ubiquitous when the word Tetra is used, Paracheriodon innesi, the Neon Tetra, leads off our list.
A diminutive one and a quarter inches, its almost surreal colors were hard to believe when it debuted. A brilliant, electric-blue band runs from the nose to tail dividing an olive back and a bright white stomach accented by a blood-red mark on its posterior half. As a large school in a properly set up planted tank, the Neon Tetra has few equals.
Neon tetras are as beautiful as they are difficult to breed. Hailing from the dark, tea colored waters of the Amazon basin, their eggs will dissolve when exposed to light. A 15 to 20 gallon tank filled with water dosed with a commercial black water extract and mild filtration, furnished with dead leaves on the bottom, driftwood and small, rounded stones should be the setup for breeding. When I bred these fish, I painted the outside of the tank with black acrylic save for a small window low in front, covered with cardboard. A blanket topped the tank. One must use real ingenuity in breeding this family of fishes, but of all of them, Neons and their close cousins Cardinals (P. axelrodi) are perhaps the most challenging.
My personal favorite of the family is the Flag Tetra, Hyphessobrycon heterorhabdus. Seen in a bare pet store tank they are less than impressive, but given proper surroundings and some time to settle in, they are one of the most attractive glittering gems of the smaller Tetras. No book or internet photo can do this little fish justice. A dark background and substrate, floating plants in a well planted aquarium will reward the keeper with a 1 3/4 inch showpiece. A brilliant band of red, gold and black culminates in a fiery red upper eye. A silvery tummy and an light olive back have a translucent quality which is difficult to describe. When caught in the right light, a little white hook is visible on the tip of the anal fin and white tail tips of the males. The females lack the white marks, and are just a hair bulkier and perhaps not quite as translucent as the males. The fish are egg scatterers that prefer to breed over fine-leaved plants. The parents are very good at eating them as they fall, so the keeper must intervene and remove the breeders promptly when breeding is complete. To distract them from the eggs until you can remove the parents, its a good idea to introduce several Daphnia to the tank while the fish are breeding. Their colors are truly stellar when fed Daphnia and Dropsilia a few times a week.
Appearing to be carrying a neon-red light from within, the Glowlight Tetra, Hemmigrammus erthrozonus is a great schooler for the new Tetra keeper. An electric-red line at the middle of the fish terminates in a red upper eye. In mature fish, the dorsal fin can have the same red on the first few rays. The fish is partially translucent, save for the silvery sack containing the organs. Glowlights top out at 1 3/4 inches. In a dark bottomed tank with a deep green or blue-black background, Glowlights winding through the plants en masse is a sight few will forget. Quite hardy when well cared for, Glowlights show best as the single Tetra species in the tank. Very free breeders over fine-leaved plants, Glowlights are a prime candidate for a first Tetra bred. Rather than the normal scatters, Glowlight pairs lock fins side by side and do a funky little barrel roll as the eggs and milt are expelled. This is repeated until there are roughly 100 eggs in the plants.
As glittery as their namesake, Diamond Tetras, Moenkhausia pitteri, are a larger tetra species for the larger tank. Seen in the store they are often washed out and unimpressive, but sympathetic surroundings and time will reward the keep with a ‘fish of distinction’ according to Innes (William T. Innes, Exotic Aquarium Fishes, 1953). The fish are a glistening sliver, with each scale tipped with green sparkles. When the fish mature, the dorsal and anal fins of both sexes elongate, and exceptional specimens can be flushed in a deep violet with blue and green sparkles. Upper eye is a fiery red. Males have larger and more pointed fins than females. Diamond Tetras reach 2.5 inches, and they are stately, passive fish. For people who like their fish calming, Diamond Tetras fit the bill. Photos are insufficient to the gorgeous living fish. They are egg scatterers like most tetras, but are rarely bred by hobbyists.
Hailing from Panama is the Platinum Tetra, Gephyrocharax atracaudatus. Though simply a glistening silvery fish and fairly difficult to find in stores, a group of these fish is usually used as a complementary species to a smaller, more colorful and numerous species in the planted tank. Unusual, a school of these fish always brings questions and complements as they stand out so in a planted tank. What makes Platinum Tetras special are a pair of bright silvery satiny spots at the base of the tail. The spots are bordered on the outside of the spots by a pair of black lines. The silvery spots reflect all sorts of blues and greens, and at times its difficult to nail down what color they actually are. Platinum Tetras prefer a level in the lower middle, and like to stay in groups of a dozen or more. They reach three inches, but are harmless to fish too large to eat. A lively, graceful, lovely fish. Very striking in a well planted tank with their glistening bodies. I use them to complement a large school of heterorhabdus. I haven’t bred them, but I assume they are standard egg scatterers.
An immediate hit and saddled with a catchy name, Head and Tail Lights (Hemmigrammus ocellifer) is our next schooling fish. A luminous, electric red-gold mark at the top of the base of the tail and a bright red upper eye caused an inventive keeper to give them that common name. Reaching 1 3/4 inches, Head and Tail lights are a gregarious, happy looking little fish, as the fins are always smartly spread. They are hardy little guys and girls, thus excellent for the newer keeper. Males are slimmer, their dorsal fin is more pointed, and a little white spot (egg spot) is in the lower middle of the anal fin. Otherwise, the sexes are colored the same. Native to Guiana and the Amazon, Head and Tail Lights are probably the easiest tetra to breed. A good-sized school spawns almost constantly. Fine leaved plants should be used in a spawning tank if you want to try your hand at spawning this fish.
A delicate, glass-like body and a blush of red in the fins typify the Glass Bloodfin of the Amazon basin. Not as tender as they look, Glass Bloodfins (Prinobrama filigera) have a reflective quality like oil on wet glass, and thus bounce colors (mainly blues) back at the keeper. The first ray of the anal fin is bright white. Partially translucent, the spinal column running along the lateral line (the line that divides the top half of the fish from the bottom) is yellowish. The eye is a slivery yellow. They grow to 2 inches. Glass Bloodfins like to be in large groups, and rather prefer hang in space together. They are surprisingly quick to food. For people who like their fish restful and beautiful, Glass Bloodfins are perfect. A lovely fish; I highly recommend them for a planted tank. They are quite hardy despite their appearance.
They spawn over plants, but don’t spawn very often. In 35 years I’ve bred them exactly twice after many, many tries.
Named for Margaret Carnegie of the famous family, Carnegiella strigata, the Marbled Hatchetfish is a Tetra for the upper realms of your planted tank. In realty a sort of flying fish, Marbled Hatchets have long pectoral fins and a narrow body like an ax head or keel of a boat. The color is golden and glistening. Brownish, parallel strips run diagonally from the sharp, ax-like belly to the top. The very top of the fish is olive. The mouth points upwards as they are surface feeders. They absolutely love live, wingless fruit flies. I dust the flies with a powdered substance containing asthaxin (NaturRose is a brand) as it intensifies their colors. They will also attack and consume a freshly-swatted, stunned housefly or any small, flying insect. They are very, very quick to the food. They grow to 1 3/4 inches. Needless to say the tank must be covered with a glass or plastic top, as while breeding or just because they want to, they can sail right out of the tank. They do best in the upper 70’s, but for breeding, the temperature should be slowly be raised to the mid-80’s (say, 83 to 85) over a few weeks in Spring. The pair spawn differently than the previous species. The male courts her by circling her rapidly. If she accepts him they jump out of the water together several times before getting side by side over fine-leaved plants. Several eggs are expelled and fertilized as they fall. Mine don’t touch their eggs, but I remove the parents to be safe. It takes about a month for the fry to resemble their parents.
One of the very few tetras that prefer slightly harder water, the Bloodfin, Aphycharax anisitsi of Argentina, has been an aquarium favorite for many decades. A silvery fish, Bloodfins have deep crimson markings on the tail, dorsal, ventral and anal fins. The pectoral fins are transparent. Bloodfins reach 1 3/4 inches. They are adaptable, but to breed they need neutral, bright water that is moderately hard, say gH 10 ppm or so. A very, very peaceful fish in groups. You can keep them in your soft, slightly acid water as they resist disease better in it, but to breed them, you’ll need to harden the water a bit. If kept in a large group, the school often stays relatively tightly together. They will scatter, however, when food is added to the tank, and they pursue live Daphnia with gusto. After the food is consumed, they spend considerable time looking around to see if they missed any.
Looking like a stretched-out tetra, the aptly-named three-lined pencilfish, Nannostomus trifacitus, winds up our list. Mature and in health, trifacitus is one of the most colorful of the smaller tetras. A golden body is marked by a deep black stripe down the middle of the fish, bisecting the eye, with thinner stripes at the top and bottom. The red on the dorsal, pectoral and anal fins is nothing short of striking; a deep, blood red. Mature males often have little red dots between the middle and upper stripes. Males are more narrow than females, which lack the red dots but their fins are just as red as the males. One must exercise patience with these fish, as they must mature to display full colors. They do best in tanks planted with tall, tape-like plants like Vallisneria. They are a stunning picture in groups and are very passive (unless you’re a Daphnia). They do not do well with busy, active fish save for Corydoras. They like to spawn on/in Riccia, and it doesn’t seem to matter if its floating or attached to driftwood or stones. The eggs are very sticky and in the breeding fever, they can be on any plant, and even on the tank glass. The parents don’t touch them normally unless they are very hungry. They should be removed, regardless. The fry look like tiny glass splinters. If fed and housed properly, they become adults in about six months. Mine bred at 76 degrees.
There are literally hundreds of species of tetras; dozens of them are available in fish stores, and more can be found with a little searching. Thus, this list is necessarily short and is limited to what came to mind as I was writing it. I’ve kept many dozens of species over the years, and still do. They are peaceful, beautiful little fish.
I encourage you to do further research on the species I’ve listed, and hope that you, too, fall under the spell of Tetras.
References: Dr. Axlerod’s Atlas of Freshwater Aquarium Fishes (Dr. Herbet R. Axelrod, et. al.), 10th Edition, TFH Publishing, 2004
Encyclopedia of Exotic Tropical Fishes for Freshwater Aquariums (Glen S. Axelrod, Brian M. Scott), First Edition, TFH Publishing, 2005
Exotic Aquarium Fishes (William T. Innes), 15th Edition, Innes Publishing Company, 1953