Cardinal tetra care
Paracheirodon axelrodi · Rio Negro and Orinoco blackwater streams
Cardinal tetras need a 20 gallon or larger tank, warmer water than neons (73 to 81 °F), soft acidic water and a group of eight or more.
- Tank size
- 20 US gal or larger
- Temperature
- 73 to 81 °F (23 to 27 °C)
- Group size
- 8 or more
- Temperament
- Peaceful
- Adult size
- 1.2 in
- pH
- 5 to 7
- Hardness (GH)
- 1 to 6 dGH
- Lifespan
- 4 to 6 years
- Diet
- Omnivore
- Care level
- Moderate
In a 20 gallon long
30¼ × 12½ × 12¾ in outsideHow to keep cardinal tetras
Cardinal tetras need a 20 gallon or larger tank, warmer water than neons (73 to 81 °F), soft acidic water and a group of eight or more. The red runs the whole length of the belly, which is how you tell them from neon tetras. They are less forgiving of hard water and new tanks, so add them to a stable, planted tank.
Diet: Omnivore: micro pellets, flakes, frozen bloodworm and brine shrimp. Fish food types compared · how often to feed.
Where they swim: Middle of the tank.
Cardinal tetra tank mates
Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.
Crystal red shrimp
1.2 in · 10+ gal · 62–76 °F
DrawingRed neon blue-eye
1.2 in · 10+ gal · 74–82 °F
Clown killifish
1.4 in · 5+ gal · 72–80 °F
Salt-and-pepper corydoras
1 in · 10+ gal · 72–79 °F
Thai micro crab
1 in · 5+ gal · 70–82 °F
Spotted blue-eye
1 in · 10+ gal · 75–82 °F
Marbled hatchetfish
1.5 in · 20+ gal · 75–82 °F
Medaka
1.5 in · 10+ gal · 65–82 °F
Keep apart
White cloud mountain minnow: No shared temperature: cardinal tetras need 73 to 81 °F, white cloud mountain minnows 64 to 72 °F.
Angelfish: Adult angelfish eat fish under about 2 in; cardinal tetras grow to 1.2 in.
Pea puffer: Pea puffers belong in a tank of their own.
Fancy goldfish: Adult fancy goldfish eat fish under about 2 in; cardinal tetras grow to 1.2 in.
Convict cichlid: Adult convict cichlids eat fish under about 1.5 in; cardinal tetras grow to 1.2 in.
Electric blue acara: Adult electric blue acaras eat fish under about 1.5 in; cardinal tetras grow to 1.2 in.
What a cardinal tetra tank needs
A tank of 20 US gallons or more (such as the 20 gallon long) with a cover, and the equipment below.
As an Amazon Associate I earn from qualifying purchases.
Aquarium Co-Op Easy Flow Sponge Filter, Small
A sponge filter gives gentle flow and cannot pull in small fish. It runs from an air pump, with airline tubing and a check valve, all sold separately.
Aqueon PRO QuietFlow Power Filter 10
Rated by the maker for up to 20 US gal, which covers a 20 gallon cardinal tetra tank without being built for a far bigger one.
Aqueon QuietFlow Internal Power Filter 15–30 gal
Rated by the maker for 15–30 US gal, which covers a 20 gallon cardinal tetra tank without being built for a far bigger one.
hygger Precise Aquarium Heater 100W
Cardinal tetras need 73 to 81 °F; most homes run cooler, so a heater holds the temperature.
API Freshwater Master Test Kit
Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding cardinal tetras.
Seachem Prime 100 mL
Removes chlorine and chloramine from tap water at every water change.
Fluval Edge Thermometer
Shows the water temperature at a glance, so you know it stays within 73 to 81 °F.
More choices, each with the reason it is in or out: Filters for a 20 gallon tank · Heaters for a 20 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →
Common cardinal tetra problems
- Most cardinals are wild caught; expect a few early losses and quarantine new fish.
- Kept too cool they lose color and fall ill; keep them with fish that like the same warm water.
- Very hard or alkaline water shortens their life.
Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.
More to compare
Sources
Name, origin and adult size checked against Wikipedia: Paracheirodon axelrodi. Temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.
Photo credits
Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.
- Cardinal tetra CHUCAO, CC BY-SA 3.0, via Wikimedia Commons
- Crystal red shrimp DirkBlankenhaus, CC BY-SA 3.0, via Wikimedia Commons
- Clown killifish Dornenwolf, CC BY 2.0, via Wikimedia Commons
- Salt-and-pepper corydoras D.W., CC0, via Wikimedia Commons
- Thai micro crab Sean Murray, CC BY-SA 2.0, via Wikimedia Commons
- Spotted blue-eye Der Regenbogenfisch, CC BY-SA 3.0 de, via Wikimedia Commons
- Marbled hatchetfish Sven Kullander, CC BY-SA 4.0, via Wikimedia Commons
- Medaka Seotaro, CC BY-SA 3.0, via Wikimedia Commons
- White cloud mountain minnow Petrtyl, CC BY 4.0, via Wikimedia Commons
- Angelfish Citron, CC BY-SA 3.0, via Wikimedia Commons
- Pea puffer Beta Mahatvaraj, CC BY-SA 4.0, via Wikimedia Commons
- Fancy goldfish Benson Kua, CC BY-SA 2.0, via Wikimedia Commons
- Convict cichlid S. Olkowicz, CC BY 2.5, via Wikimedia Commons
- Electric blue acara 5snake5, CC0, via Wikimedia Commons
- Neon tetra Holger Krisp, CC BY 3.0, via Wikimedia Commons
- Black neon tetra Debivort, CC BY-SA 3.0, via Wikimedia Commons
- Green neon tetra Sascha Biedermann, CC BY-SA 2.5, via Wikimedia Commons
- Ember tetra Klaus Rudloff, CC BY-SA 4.0, via Wikimedia Commons
.jpg){kind=link}
.jpg){kind=link}
.jpg){kind=link}
