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SESK: Stuff Everyone Should Know · sesk.info/fish-cichlid-aggression

Merck says aggression toward newly added fish is common among which freshwater fish?

Cichlids and other larger freshwater fish.

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  1. Small schooling tetras
  2. Small rasboras
  3. Cichlids ✔

Why: Merck says aggression toward new fish is common among freshwater cichlids and other freshwater fish over about 3 inches long. Bullying stresses every fish in the tank.

Huh, didn't know that: Merck says fish like cichlids need enough room for each fish to have its own territory.

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References

Answer: Cichlids. Merck says aggression toward new fish is common among freshwater cichlids and other freshwater fish over about 3 inches long. Bullying stresses every fish in the tank.

  1. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    Aggressiveness toward new fish is common among freshwater cichlids and other larger (more than 3 inches [7.6 cm]) freshwater species
    Checked 2026-10-11.
  2. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    Aggressive behavior is stressful for all fish in the tank
    Checked 2026-10-11.
  3. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    This is particularly true when space and territory in the aquarium are at a premium.
    Checked 2026-10-11.
  4. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    While the bag is floating, rearrange the decorative objects in the tank.
    Checked 2026-10-11.

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