Emperor Tetra Quick Stats
Minimum Tank Size: 20 Gallons (76 Liters)
Care Level: Very Easy
Water Conditions: 5.0-7.5 pH and Soft to Moderately Hard
Temperature: 75-82°F (24-28°C)
Maximum Size: 2 ½ “(6 cm)
The emperor tetra (Nematobrycon palmeri) is a small, peaceful freshwater fish, commonly available in the aquarium hobby. Emperor tetras are considered to be one of the best fish for community tanks, and they do well with most species of non-aggressive fish.
Native to Columbia, these fish are endemic to the Atrato and San Juan river basins. They are primarily found in clear, slow-moving streams and rivers, with sandy, rocky, or muddy bottoms.
On average, these fish will live between 3-5 years in a well-maintained aquarium, but there are reports of some specimens living longer. Emperor tetras grow to a maximum size of 2 inches (5 cm), with the males being slightly larger than the females.
Housing Emperor Tetras
Emperor tetras should always be kept in groups of at least six, but ideally, should be kept in groups of ten or more. When kept in larger groups, these fish exhibit impressive shoaling behavior and have lower levels of stress.
If emperor tetras are kept in a species only aquarium, then they should be housed in at least a 20-gallon (76 liters) fish tank. However, since most are kept in community tank setups, a 29-gallon aquarium is usually viewed as the bare minimum for a small shoal of emperor tetras and another species of fish.
While many of the emperor tetras available for sale are wild caught, the majority seemed to come from fish farms these days. Because of this, most will be able to adapt to a wide range of water types, though it’s still recommended to provide soft and acidic water if possible. Read How to Safely Lower the pH in an Aquarium here.
The aquarium should have a dark substrate – preferably sand or gravel – with plenty of ornaments, driftwood, and live plants. The males are sometimes territorial (though the fights rarely result in any injuries) and decorations like driftwood help to break their line-of-sight and reduce aggression.
Filtration for Emperor Tetras
When it comes to filtration, the best option is usually a hang-on-back filter (HOB). A well-maintained HOB filter will keep an aquarium’s water in excellent condition and is more affordable than most other options. One of the best filters on the market is the Aquaclear Power Filter, and they are incredibly sturdy – often lasting years without problems – and are also known for their excellent filtration.
Feeding Emperor Tetras
The emperor tetra is primarily a predator in the wild, feeding on larvae, small invertebrates, and insects. In the aquarium, their diet should be comprised of a high-quality flake food, with regular offerings of live and frozen foods.
One of the best flake foods for emperor tetras is Hikari Micro Pellets, which are specifically designed for small-mouth fish. This food provides important nutrients and will help the fish obtain their full coloration.
When it comes to live and frozen foods, they will hungrily devour live bloodworms, daphnia, brine shrimp, mosquito larvae (illegal to culture in some areas), and blackworms (tubifex in Europe). Their tastes are similar in frozen foods, and frozen bloodworms, daphnia, and brine shrimp are all eagerly accepted.
Breeding Emperor Tetras
Emperor Tetras are quite easy to sex, with the males being larger and more colorful than the females. The males will develop a longer anal fin and more pointed dorsal and caudal fins as they mature. Also, another easy way to differentiate the sexes is that the male’s irises are blue around the pupil, while the female’s are a green coloration.
These fish are relatively easy to breed in the home aquarium, but for any significant number of fry to survive, a separate breeding tank should be provided. The breeding tank should be dimly lit with soft and acidic water.
The more traditional breeding tank setup is to leave the tank bare except for a substrate of marbles along the bottom. The eggs will fall into the spaces between the marbles, so the adults won’t be able to eat them. However, some people use a layer of mesh along the bottom of the aquarium and claim it is more effective at keeping the eggs safe.
Another option is to provide a standard aquarium setup for the breeding tank, with soft, acidic water, a dark colored substrate, and dense aquatic plant coverage. The plants should be finely leafed such as Water Sprite or Java moss, to give the fish a place to deposit their eggs. An alternative to live plants is to use spawning mops, though live plants are generally preferred.
Before spawning, the males and females should be placed into separate tanks. The separated males and females should then be conditioned with live foods for at least a week. Once the females begin to plump up with eggs, a single male and female should be placed in the breeding tank.
The fish will usually spawn within a day or so, and if no spawning occurs, they should be removed, and another conditioned pair added to the breeding tank. After the fish have spawned, the adults should be removed to keep the eggs safe. It’s important to note that spawning can take several hours, so make sure the fish have completed mating before removing the adults.
The eggs will normally hatch after two to three days and become free swimming on day five or six. Once the fry are free-swimming, they should be fed infusoria. After about a week, they can be moved onto baby brine shrimp or microworms, and then finely powdered flake food.
These fish are compatible with a wide range of peaceful fish and will do well with dwarf cichlids (German Blue Rams, Kribensis cichlids, and Bolivian Rams), corydoras catfish, livebearers (Guppies and Platies), Zebra Danios, gouramis, and most species of peaceful tetras. Overly active fish should be avoided, as should any fish large enough to see the emperor tetras as prey.