The Red Mouth Headstander can assume an almost vertical position and flip upside down to grasp food from the substrate!

The Red Mouth Headstander Anostomus ternetzi is an intriguing aquarium fish. It is moderate in size, typically growing to about 4 3/4 inches (12 cm) in length, though some specimens may reach about 6 1/3 inches (16 cm). It has an elongated, somewhat rounded body shape. Its body is patterned with a brownish, lightly striped upper band and two darker lower bands running horizontally, and they are interspersed with narrow lines of pale yellow. Some other common names for A. ternetzi are Goldstripe Headstander, Ternetz’s Anostomus, and simply Headstander.

The Red Mouth Headstander is an interesting member of the Anostomus genus. In the wild, this fish is found in shallow streams with strong currents where theirs lots of algae and small invertebrates to feed on. This fish gets the name “headstander” from its tendency to rest almost vertically, usually at about a 45 degree incline, with its head down in the rocky fissures of fast flowing waters.

Like the other headstanders, it is characterized by a small, tapered head with an upward pointing mouth. The mouth is well suited for easily taking food from the middle or upper water levels, or at the surface. But it will also take food from the bottom, and it can flip upside-down to pick up such tasty morsels.

There are currently 5 species in the Anostomus genus, but only the the Red Mouth Headstander and Striped Headstander A. anostomus are well-known in the aquarium hobby. Though these two are very similar in appearance, they can be distinguished by their coloring unless they are washed out due to stress.

The Striped Headstander A. anostomus has three broad black horizontal bands, with the middle and lower bands having a zigzag border. The interspaces between these bands are pale peach to pinkish stripes and there is bright red on the fins. The Red Mouth Headstander has a similarly banded pattern, but the upper band is more brownish, and it mostly lacks red tinting on its fins, though the tip of its snout is red. There is also no zigzag on the borders of the lower two bands and the interspersing light stripes are a more golden color.

This Red Mouth Headstander is not quite as remarkable in color as its more striking relative, the Striped Headstander, but it is not as sensitive to aquarium conditions and is less territorial. It is also smaller and can live a couple years longer in captivity. Overall, it is a fairly hardy fish as long as its water is kept clean, but it is best kept by an aquarist with some fish keeping experience.

This active fish attains a good size, so needs an aquarium of at least 30 gallons or more. This fish tends to be shy when first introduced to an aquarium and will prefer some planted areas, some layered rocks, and a darker gravel. Though generally calm, like all headstanders, it is sensitive to shadows and likes to jump, so be sure to keep the aquarium covered.

This species is mostly a peaceful community fish, but it can be slightly aggressive. It can be kept singly, but it also does fine with its own species when kept in a group. To keep down aggression, a group of 6 or more works best. This fish makes a good companion with other community tank mates that are the same size or larger.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Characiformes
  • Family: Anostomidae
  • Genus: Anostomus
  • Species: ternetzi
Headstander – Quick Aquarium Care
  • Aquarist Experience Level: Intermediate
  • Size of fish – inches: 6.3 inches (16.00 cm)
  • Minimum Tank Size: 30 gal (114 L)
  • Temperament: Peaceful
  • Aquarium Hardiness: Moderately hardy
  • Temperature: 73.0 to 82.0° F (22.8 to 27.8&deg C)
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Habitat: Distribution / Background

The Red Mouth Headstander Anostomus ternetzi was described by Fernández-Yépez in 1949. It is found in South America in Brazil in the Amazon River basins of Orinoco, Rio Araguaia, and Rio Xingo as well as in the coastal rivers of Guianas.This species is not listed on the IUCN Red List. Its common names included Ternetz’s Anostomus and Goldstripe Headstander, as well as just Headstander.

About the Anostomus Genus:

This species is a member of the Anostomidae family, commonly called Anostomids, which contains about 150 species. These are freshwater fish found in nearly every major body of water in South America, except for the upper regions of the Andes Mountains. They occur from the Río Atrato in the north down to central Argentina, with a few found west of the Andes mainly in Colombia and Venezuela.

The Anostomids have a moderately elongated, and somewhat rounded body with the head tapering into a rather long, straight snout. They mostly grow between 5 3/4″ to 23 1/2″ (15 – 60 cm) in length, but a few can reach a maximum size of 31 1/2″ (80 cm). They are considered an edible fish and some of the larger species are regularly caught for food.

Many Anostomids are referred to as “headstanders” because they habitually swim with their heads pointing downwards, angling from 45° to 90°s. The scientific name, Anostomidae, describes their mouth opening. It’s derived from ancient greek with the term “ano” meaning “up” and “stoma” meaning “mouth.” Their upturned mouths are small, and Immediately at or near the tip of the snout. Most graze on plants and algae near the bottom, but some also pick up detritus and tiny invertebrates living in the substrate. Actually, a number of other fish species from South America are known as headstander fish. There are also headstanders from the Chilodus genus of the Chilodontidae family.

Within the Anostomidae family, this species is placed in the Anostomus genus. The Anostomus genus currently has 5 recognized species, though only the Red Mouth Headstander A. ternetzi, and Striped Headstander A. anostomus are well-known in the aquarium hobby. This small genus of fish are found in the Orinoco and Amazon Basins, as well as various rivers in the Guianas. Large shoals are typically found along the shores of rivers and streams. They dwell in nearly vertical rocky fissures in shallower areas, where the water is fast-moving and the algae is at its best.

About the Red Mouth Headstander:

The Red Mouth Headstander, like others of its genus, inhabits the shallow rocky shores of rivers and streams in areas of fast-flowing water. In nature it occurs in the middle area of open water and along the banks where there is dense semi-suspended groundcover of roots and submerged branches that form a very dark tangle. They will spawn on the vegetation and on the bottoms of the streams.

They live in large shoals and graze on algae and stalked plants. These omnivorous fish feed on aquatic plants, algae, small invertebrates, and insects. A single specimen can be kept in a community with other peaceful medium to large fish. Although they live in large groups in the wild, in the aquarium they will become aggressive with conspecifics if kept in a small school. They will tolerate each other, however, when kept in groups of 6 or more in larger aquariums.

  • Scientific Name: Anostomus ternetzi
  • Social Grouping: Groups – They occur in large shoals in the wild.
  • IUCN Red List: NE – Not Evaluated or not listed


The Red Mouth Headstander is an elongated fish with a pike type body, though more rounded. It is characterized by a small tapered head with an upward pointing mouth. True to its name, it will spend a good deal of its time in a “head-down” position at an angle of 45° or more. This fish will typically reach almost 4 3/4 inches (12 cm) in length, though some specimens may grow as large as 6 1/3 inches (16 cm), and has a lifespan of 5 to 8 years.

Its body has three dark horizontal bands with the interspaces between being whitish to intense yellow, or golden color. This patterning runs the entire length of the body, from the snout to the caudal peduncle. The middle and lower bands are black, but the upper band is more of a brownish area with light centered scales that form longitudinal lines. The tip of its snout is red, thus the name “red mouth,” and Its fins are transparent, sometimes with a light brown or reddish-brown cast. Younger fish are paler.

  • Size of fish – inches: 6.3 inches (16.00 cm) – They typically grow to about 4 3/4 inches (12 cm), though some reach 6 1/3 inches (16 cm),
  • Lifespan: 8 years – They have a lifespan of 5 to 8 years in the aquarium.

Fish Keeping Difficulty

The Red Mouth Headstander is a fairly hardy fish and recommended for an aquarist with some fish keeping experience. It is relatively sensitive to changes in water chemistry, so the water quality should always be maintained. The tank needs strong filtration that provides good water movement, to simulate its natural environment.

It is shy, so for the best results, keep it in a covered tank with lots of hiding places provided with a decor of rocks and driftwood with some algae to feed on. A planted aquarium works great too, but make sure there is plenty of algae for it to feed on, or it will nibble on the plants.

  • Aquarium Hardiness: Moderately hardy
  • Aquarist Experience Level: Intermediate

Foods and Feeding

In the wild the Red Mouth Headstander will feed on algae, aquatic plants, insects, and small invertebrates. In the aquarium, these omnivorous fish will generally eat all kinds of live, fresh, and flake foods. To keep a good balance, give them a high quality flake food every day along with a good spirulina formula fish food or algae wafer. Feed brine shrimp (either live or frozen) or blood worms as a treat.

They will also enjoy other vegetable matter such as chickweed, watercress, crushed lettuce leaves, and spinach leaves. Be warned that they may nibble on the soft shoots and leaves of aquarium plants, especially if there is not enough algae growth in the tank. They do best when fed several times a day. Offer only what they can eat in 3 minutes or less at each feeding.

  • Diet Type: Omnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Some of Diet
  • Feeding Frequency: Several feedings per day – Offer only what they can consume in 3 minutes or less with multiple feedings per day.

Aquarium Care

Red Mouth Headstander is not exceptionally difficult to care for provided their water is kept clean. Aquariums are closed systems, and regardless of size, all need some maintenance. Over time, decomposing organic matter, nitrates, and phosphate build up and water hardness increases due to evaporation. To combat these ever-changing conditions, water should be replaced on a regular basis, especially if the tank is densely stocked. At least 25 to 50% of the tank water should be replaced every other week.

  • Water Changes: Bi-weekly – Change 25 to 50% of the tank water every other week.

Aquarium Setup

The Red Mouth Headstander is somewhat less demanding than its cousin the Striped Headstander A. anostomus, and can be kept singly or in a group. Although is is found in large shoals in nature, it tends to be very quarrelsome with conspecifics if the group is too small, so group should consist of 6 or more individuals. It also gets pretty big and will need at least a 30 gallon (114 L) aquarium or larger for a single specimen. A group of 6 will need 50 gallons (190 L) or larger.

The tank should have a powerful filtration system that will simulate the strong currents found in the wild. A River Manifold system can be installed to give this fish a good current. However, a canister filter and powerheads can be used in place of a manifold system if preferred. Make sure the tank has a tight fitting cover as these fish are great jumpers.

This is a very shy fish when someone approaches the tank, especially when first introduced. After a few days, however, this fish will lose its timidity if provided with appropriate hiding places. It will need a spacious, well planted tank with a decor that offers plenty of hiding places and a darker substrate.

This fish does well in a biotype tank setup. Along the banks of the streams in its natural habitat, the roots and submerged branches create a very dark tangle. For a biotype setup, the substrate should be a soft river sand. This is a very shy fish that likes some planted areas along with piles of rocks and driftwood to create shelters at mid-height, and some should penetrate the water surface. Adding some floating plants over the sheltering area will help dim the light. But also have some free space on the surface area with bright light to encourage algae growth, which will be a great supplemental food. Keep in mind that if you add plants to the tank fish may eat them, especially the new soft shoots and leaves.

  • Minimum Tank Size: 30 gal (114 L) – A group will need a 50 gallon (190 L) aquarium, or larger.
  • Suitable for Nano Tank: Yes – One individual can be kept in the largest sized nano tank.
  • Substrate Type: Small Gravel – This fish appreciates dark, small gravel or sand.
  • Lighting Needs: Moderate – normal lighting – Brighter lighting is needed to produce good algae growth for they to graze on.
  • Temperature: 73.0 to 82.0° F (22.8 to 27.8&deg C)
  • Breeding Temperature: 77.0° F – These fish spawn between 77 to 82° F (25 – 27° C).
  • Range ph: 6.4-7.2
  • Hardness Range: 5 – 16 dGH
  • Brackish: No
  • Water Movement: Strong – A strong current will imitate their natural environment.
  • Water Region: Middle – These fish will swim in all areas, but primarily at the bottom and middle of the aquarium.

Social Behaviors

The Red Mouth Headstander is a peaceful schooling fish that can be kept in a community. They can be kept singly or in a group, but Individual fish will mark out territories and In too small group they can become aggressive. To cut down on aggression, keep them in a group of at least 6 or more of their own kind and provide a hiding place for each individual. When kept in groups, they do tend to hide more than when kept singly.

They are good for a community aquarium with other peaceful fish that are the same size or larger. Some good tank mates are other short finned characins and peaceful cichlids. Avoid fish that demand the same foods, however, as the Red Mouth Headstander may not fare well with competition. For example it may not do well with catfish from the genus Hemiancistrus, the Chinese Algae Eaters of the Gyrinocheilus genus, or freshwater sharks from the genus Epalzeorhynchos. If frightened, they will immediately try to jump out of the tank, so have a tight fitting top on the aquarium.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes – They can be kept in groups of 6 or more of their own kind as long as each fish has its own hiding place.
    • Peaceful fish (): Safe – Aggressive towards smaller fish, but a good community fish with tankmates of the same size or larger.
    • Semi-Aggressive (): Threat
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Threat
    • Large Aggressive, Predatory (): Threat
    • Monitor
    • Shrimps, Crabs, Snails: Safe – not aggressive
    • Plants: Monitor – They may eat soft plants and shoots if their diet does not provide sufficient vegetable foods.

Sex: Sexual differences

Mature females tend to be rounder-bellied than males.

Breeding / Reproduction

In nature, Headstanders are spawning fish that shed their eggs after pairing at the surface. The Red Mouth Headstander A. ternetzi will spawn on vegetation and on the bottoms of the streams. Breeding Anostomus species has been accomplished in captivity, but no firm data is available. There are currently no reports of of the Red Mouth Headstander having been bred in the aquarium. Successful breeding of Anostomus is very rare, and no method has yet been proven effective. The diet of the fish seems to play a very important role in initiating a spawn.

For a chance at successfully breeding them, separate the males from the females. Condition them by feeding them live foods. Provide a large spawning tank that is at least 3 1/3 feet (1 m) long with a sandy bottom, a few roots and stones with algae, and some peat filtration to add a touch of acid. Suggested water parameters are a pH between 6 and 7, a hardness of 10° KH, and a temperature that matches their regular tank.

Introduce the males and females into the prepared tank and gradually increase the temperature to between 77 and 82° F (25 to 27° C). Cover the top with a towel, creating a darkened environment to help trigger the spawn. Pairing should occur quickly just below the surface of the water. The female will release 3 to 5 eggs that are 1.5 mm in size. Following the spawn, remove the parents from the tank as they have a tendency to eat the eggs. Feed the newly hatched fry brine shrimp nauplii, Cyclops, and algae.

The method above is a compilation of suggestions, including information from authors Dr. Rudiger Riehl and Hans A. Baensch in their book, Aquarium Atlas Vol. 1 (1991). In the breeding section of the species Anostomus anostomus, they point to breeding of the closely related Spotted Headstander Chilodus punctatus. The spawning tank decor and parameters above are derived from the breeding of C. punctatus in an account by Geisler, originally published in the West German Magazine DATZ. Also, see a description of breeding characin fish here: Breeding Freshwater Fish: Characins.

  • Ease of Breeding: Difficult

Fish Diseases

Headstanders are hardy and disease is not usually a problem in a well-maintained aquarium. That being said, there is no guarantee that you won’t have to deal with health problems or disease. Anything you add to your tank can introduce disease. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything you add to an established tank so as not to upset the balance.

A good thing about Headstanders is that due to their resilience, an outbreak of disease can often be limited to just one or a few fishes if dealt with at an early stage. When keeping more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your Red Mouth Headstander the proper environment and a well-balanced diet. The more closely their environment resembles their natural habitat, the less stress the fish will have, making them healthier and happier. Stressed fish are more likely to acquire disease.

As with most fish, they are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. Aquarists should read up on common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.


The Red Mouth Headstander is occasionally available in pet stores and online and is moderately priced.