Tetra Fish Care Sheet | PetMD

Tetra Fish Species Overview

This care sheet outlines basic care needs for a variety of tetra species, including: 

• Serpae tetra 

• Black neon tetra 

• Cardinal tetra 

• Black phantom tetra 

• Bloodfin tetra 

• Diamond tetra 

• Bleeding heart tetra 

• Glowlight tetra 

• Congo tetra 

• Rummy nose tetra 

Tetras are small, colorful fish that have quiet and calm temperaments. 

Tetras prefer to spend their time swimming in the middle to lower levels of the aquarium and are very active.  

To prevent pairing and aggression, maintain tetra schools of five or more that are in odd numbers.  

Tetras are omnivorous fish that need meat and plant-based foods in their diet. 

Tetra Fish Characteristics 

Tetra Fish Supply Checklist

To keep a tetra happy and healthy, pet parents should have these basic supplies on hand: 

Tetra Fish Habitat

Choosing the Right Enclosure 

A single adult from a small species of tetra (like the neon) will need a minimum of 10 gallons of tank space in their aquarium.  

You’ll need a much bigger aquarium for larger tetra species (like the Congo tetra) or a small group of tetras. As a rule of thumb, provide at least 1 gallon of extra space for each inch of fish in the aquarium. For example, five 2-inch-long tetras will need a 20-gallon tank or larger. 

All aquariums should be secured with a fitted lid to prevent escape. Always provide the largest habitat possible, as water parameters are less stable in smaller fish tanks. 

Setting Up Your Habitat 

Tetras are a schooling fish that thrive in the company of other tetras.

Tetras should be kept in odd-numbered groups of five or more fish from the same species. When kept in even numbers, tetras may pair off and become aggressive toward their tankmates. 

Schools of tetras can also be housed with a variety of other aquatic species, including: 

• Danios 

• Rasboras 

• Guppies 

• Mollies 

• Platies 

• Swordtails 

• Gourami 

• Cory catfish 

• Hatchets 

• Rainbowfish 

• GloFish

New tankmates must be introduced to an aquarium gradually, and pet parents should remember that their tank’s ammonia, pH, and nitrate levels will change when a new fish is introduced. These parameters need to be monitored carefully after adding new fish.

Fish should not be kept in overcrowded aquariums, as these conditions often lead to stress and disease in the tank. 

Filtration 

A filter system is an essential addition to any fish tank. In addition to keeping tanks clean, filters remove harmful toxins like ammonia from the aquarium’s water and add oxygen to the water so fish can breathe.   

Power filters (also known as “hang-on-back” filters) and external canister filters are recommended because they offer effective mechanical, biological, and chemical filtration and don’t take up space inside an aquarium. Generally, tetras prefer water with slow to moderate circulation. 

Tip: An aquarium’s filter should be powerful enough to process all the water in the tank at least four times an hour. For example, a 20-gallon tank should ideally have an aquarium filter with a flow rate that’s at least 80 gallons per hour (GPH). If only a 50 or 100 GPH filter is available, pet parents should always size up and purchase the 100 GPH option. 

Water Health  

Pet parents should test their aquarium’s water regularly to ensure its pH, ammonia, nitrate, and nitrite levels are stable and within a safe range. An aquarium test kit can be used to measure key water parameters quickly and accurately. 

Many tetra species benefit from the addition of freshwater salt to their aquarium. If it is added to the tank, the water’s specific gravity should be kept at 1.004 and should not change more than +/- 0.001 in 24 hours. Pet parents must research the needs of the specific species of tetra they’re caring for before adding freshwater salt to their habitat.  

A hydrometer or refractometer (salt level tester) should be used to measure the salt concentration and specific gravity of the aquarium’s water. 

Temperature 

Tetras prefer warm water that’s between 72 and 82 F. The water’s temperature should not fluctuate more than +/- 2 degrees in 24 hours. 

Pet parents should install an aquatic heater that’s controlled with a thermostat in their aquarium to keep the water’s temperature in the ideal range. An aquarium thermometer should be used to check the tank’s water temperature daily. 

When selecting a heater for their tank, pet parents should keep a few things in mind: 

• Some modern heaters have built-in thermostats, while others need to be paired with a thermostat that’s purchased separately. 

• Aquarium heaters need between 2.5 and 5 watts of power for every gallon of water in a tank. This means that a 10-gallon tank needs a 25- to 50-watt heater. 

• Larger aquariums with a tank volume over 50 gallons may need two small heaters, placed on opposite sides of the tank, to prevent cold spots from developing in the water. 

Decor and Accessories 

Substrate

The bottom of a tetra’s tank should be lined with 1–2 inches of sand, gravel, or pebbles. Be sure to rinse the substrate with clean running water before adding it to the tank.   

Tetras spend most of their time swimming at the top and middle parts of an aquarium and generally don’t dig or burrow in their substrate. 

Dark-colored, sandy substrates can make tetras’ bright colors pop! 

Aquariums need about 1½ pounds of substrate for each gallon of water in the tank. For example, a 10–gallon tank will require about 15 pounds of substrate to create a 1- to 2-inch layer.   

Plants, Driftwood, and Rocks

Tetras tend to like dark, shady habitats with lots of cover. Plants, driftwood, and rocks should all be used to create natural, safe hiding places that mimic tetras’ native homes. 

Look for floating plants (like Java moss, frogbit, dwarf water lettuce, and hornwort) that can create shaded hiding places for the tetra.      

Tetra Fish Cleaning and Maintenance

Pet parents can maintain the condition of their tetra’s tank by performing routine water changes (no more than 10–25% of the aquarium’s total water volume) every two to four weeks. 

Draining and replacing the aquarium’s entire water volume should be avoided, as doing so will remove the beneficial bacteria in the tank that keep the habitat’s ecosystem healthy.  

Most aquariums will need a full cleaning once a month, depending on the number of fish/invertebrates in the tank.

Tetra Fish Diet and Nutrition

Tetras need to be fed small amounts of food one to two times per day and should not be offered more food than they can consume within one to two minutes. To stay healthy, tetras need variety in their diet and should not be fed the same food every day. 

A nutritious and well-balanced diet for a tetra consists of pellets, flakes, and frozen or freeze-dried food formulated for tropical freshwater fish.

Frozen foods must be thawed before feeding. 

Bloodworms or brine shrimp (frozen or live) may be fed as treats.

Remember: Never use a microwave to thaw or warm frozen food, and never offer food that’s still frozen to a pet. Frozen food that is not consumed should never be refrozen for future use, as this allows  bacteria to form in the food. 

Tetra Fish Care

Pet parents should change 10–25% of the total volume of their aquarium’s water every two to four weeks, or more often if needed.  

Newly added water should be at the same temperature and have the same salinity (salt concentration) as the existing water in the tank. 

After a new fish/invertebrate or new equipment is added to an aquarium, it’s important to test the tank water’s quality once a week for at least two months to ensure that its pH, nitrite, ammonia, nitrate, carbonate, and general hardness levels are in the ideal range.  

If the tests’ results are safe and consistent after two months, pet parents can decrease water testing to once a month. 

Water test kits have an expiration date and should be replaced yearly.  

Pet parents should monitor their aquarium’s water level and top it off as needed. Before being added to an aquarium, water must be treated with a water conditioner to remove toxic chemicals like chlorine, chloramines, and heavy metals.  

An aquarium’s filter, water temperature, and other equipment should be checked daily to ensure they’re working properly. Filter media should be replaced monthly or rinsed in old tank water during water changes, depending on the water condition and the number of fish/invertebrates in the tank. 

Pet parents should follow the use, care, and maintenance instructions provided by the manufacturer of their filter system.  

Do not use hot water, bleach, or chemicals while rinsing filter media. This will kill the beneficial bacteria that help keep aquatic habitats safe, clean, and stable.  

Avoid replacing all the filtration media in an aquarium at the same time, as this can also remove beneficial bacteria from the tank. 

Tetra Fish Veterinary Care

Annual Care

In a properly maintained tank of appropriate size, in which you perform your own water quality tests and water changes weekly, it is OK to contact a veterinarian only if there is a problem with your tetra. While a tetra can be transported to a vet, it’s recommended that you find an aquatics veterinarian who can make house calls, as transport is a major stress event for fish.

Signs of a Healthy Tetra

• Bright coloration

• Full range of motion of fin movement, equal on both sides

• Intact fins all the way to the edges with no discoloration

• Regular and active swim pattern

• Large appetite

• Schools when appropriate

When to Call a Vet

• Changes to the tetra’s coloration—particularly becoming dull, focal spots of change, stripes, or bands of color change

• Lethargic swimming, potentially with an abnormal pattern such as circling, listing to the side, or staying on the top or bottom of the tank.

• Receding fin edges with or without discoloration

• Decreased appetite for more than a day

• Itching

• Rapid breathing, potentially with flared gills

• Gill color changes (usually pale or red)

• Presence of lumps/bumps/masses

• White growths/spots of any kind

• Bloated appearance with scales flared outward instead of lying flat

• Bulging eyes, with or without a color change

• Consistently swimming separately from other tetras

Common Illnesses in Tetra Fish

• Ich, also known as white spot disease

• Dropsy (fluid-filled coelomic cavity)

• Parasites (including lice or leeches)

• Bacterial infections

• Fin/tail rot

• Pop eye

• Fungal infections

• Swim bladder disorders

• Cancer