Are Zebra Danios Aggressive?

The danio rerio, commonly known as the stripe danio or zebra danio, have aggressive tendencies when protecting their turf and food and when they want to show dominance. An agitated zebra danio will elevate its fins, keep its mouth ajar and make wavy motions with its body.

Zebra danios are peaceful shoaling fish that can share tank space with many other peaceful species despite occasional aggression.

Zebra Danios Are Aggressive

Aggressiveness in zebra danios is not only reserved for the male of the species. Female danios display aggression the same way the males do.

Zebra Danios Aggressiveness In The Wild

In the wild, it is all about the” turf,” the “girls,” and the food! Zebra danios will fiercely claim individual turf close to mating grounds. Once the zebra danios have established their superiority, other fish will behave submissively towards them regarding food and territory.

Wild zebra danios will enforce dominance by fiercely chasing and nipping other fish. Male zebra danios are more aggressive than females. They protect the territory against the possible “invasion” of zebra danio males in search of breeding females.

If zebra danios deem it necessary, they will deny other fish access to food. Keeping the fish away from food sources further empowers the zebra danios fish, showing more dominance over the lower-ranked species, leaving them with little to no provisions.

Soulkeeper [Public Domain]

Zebra Danios Aggressiveness In Captivity

Zebra danios, although considered calm and friendly shoaling fish, may show aggressiveness in captivity.

Factors such as poor water conditions, over or under population of the fish tank, and incorrect water parameters cause captivated zebra danios to act out.

The biggest culprit for aggressiveness in captivated zebra danios has to do with the population of the fish tank. These are shoaling fish, and they need to feel part of a shoal.

Therefore, too little interaction with other fish may lead to aggressiveness to determine dominance. In such cases, they appear to turn aggressive due to boredom.

Too many fish in the fish tank makes them anxious and frustrated since they will have difficulty establishing dominance, and they will turn to aggression to try and resolve their situation.

The nature of captured and wild zebra danios is the same. They want to protect their turf, females, and their food.

Zebra Danios Show Of Aggression

Chasing and nipping at other fish is the first sign of an aggressive zebra danio. Aggressive male zebra danios will even chase and nip at zebra danio females, in or out of breeding season.

Apart from chasing and nipping, aggressive zebra danios show distinct body language. The following are tell-tale signs of aggressiveness:

  • Elevated fins
  • Slightly open mouths
  • Wavey body motions.

Aggressive body language indicates the male zebra danio’s intention of protecting and guarding its territory and food while showing off its social superiority. Breeding males are incredibly protective of their territory and will persistently chase females during breeding.

Why Zebra Danios Chase One Another

Both female and male zebra danios may chase each other for fun, establish dominance, protect their territory, compete for food, and mating.

Male zebra danios will chase females for mating purposes. Chasing the female encourages her to lay eggs which the male then fertilizes, producing offspring.

To keep zebra danios from fighting over food, feed them adequate amounts of nutrient-rich foods to avoid malnutrition. Malnutrition will entice zebra danios to chase each other to secure food resources.

The following factors may cause zebra danios to chase each other:

  • Stress
  • Inadequate water conditions
  • An overcrowded tank
  • Incompatible tankmates

Prevent overcrowding a fish tank by allowing a gallon of water per inch of fish. Overcrowded tanks result in aggressive behavior due to stress and frustration, leading to zebra danios terrorizing their tank mates.

How To Minimize Aggressiveness In Zebra Danios

The best way to help zebra danios to be less aggressive is to pay careful attention to the aquarium conditions and choose the correct tank mates to help calm them down.

Tank Conditions That Curb Zebra Danio Aggressiveness

Provide enough shelter in the form of plants, live or artificial, for the zebra danios to use as shelter. In addition, provide rocks, driftwood, and ornaments that provide hiding places from other, perhaps more aggressive fish.

Zebra danios need time to figure out their social standing within the tank. Once their social standing is established, they will return to being the peaceful fish they are known to be and become part of the dynamics within the tank.

Keep at least four zebra danios. Zebra danios are shoaling fish and, therefore, very social. They need interaction with zebra danios and other peaceful shoaling fish to be happy.

They are great additions to communal tanks and will add vibrance and color to the aquarium once they have settled down.

Zebra Danios in Front of Plants

Water Conditions For Happy Zebra Danios

Zebra danios should be kept in tanks no smaller than ten gallons with water temperatures between sixty-four- and seventy-four degrees Fahrenheit. Keeping the pH levels between six and a half and seven and the hardiness of the water at five to twelve dGH will ensure ideal conditions for zebra danios.

Zebra danios do very well in cooler water and do not need a water heater. However, since zebra danios are tropical fish, it is recommended that the room temperature surrounding the aquarium should be kept moderate to ensure the water does not get too hot or too cold.

Zebra Danio Tank Mates

Zebra danio fish can share a tank with most other shoal fish. Perfect tank mates, apart from other danios, include cory catfish, cardinal tetras, gourami platies, mollies, and angelfish, to name but a few.

Zebra danios tend to nip at the fins of fish with long, flowy elaborate fins and tails, so for their safety and your sanity, refrain from keeping them along with your striped pajama friends. Fish with long fins and showy tails are usually slower swimmers who will be no contest for bored fin-nipping zebra danios.

As soon as you detect any aggression shown towards any tankmate, remove either the zebra danio or the tankmate as soon as possible and place them in a separate tank. Try to determine and remove the reasons for the aggressive behavior before re-introducing them back into the communal tank.

If the zebra danio continues to harass the tank mate in question, consider a way to lower the water temperature since tropical fish tend to be more aggressive in warmer water.

Warmer water conditions encourage breeding in zebra danios. Unfortunately, the breeding season brings out the worst in zebra danios. Lowering the water temperature will aid in calming them down, once again restoring peace in the communal tank.


Apart from being a little nippy and mildly terrorizing towards those they deem inferior, zebra danios are by no means lethal, and their blue and silver stripes add vibrance to any aquarium.