Why do fish fight against the aquarium wall

Territories and aggressiveness of angelfish

Angelfish are not schooling fish, they form territories. Up to 3 centimeters in diameter, they actually behave like schooling fish. In the adult stage, the swarm dissolves and the angelfish then move in a loose association in large aquariums; in pairs, but peacefully with each other through the water. During the spawning season they form territories that are fiercely defended.

Adult angelfish can become very aggressive, especially during spawning. When a pair has come together and is ready to spawn, the male and female usually stay close together. Other fish, especially other angelfish, are scared away by both of them. Scalars can accelerate enormously. In such situations it becomes clear why angelfish should be kept in aquariums with 400 to 500 liters of water. Depending on the size of the aquarium, other angelfish are literally pushed into a corner.

After a while, the couple begins to brush a wide leaf and spawn on it. By then, at the latest, many aquariums turn out to be too small for several angelfish.

When angelfish prepare for spawning, they defend their territory by all means. Competitors are bitten and chased to death very quickly. Above all, other scalars are seen as competitors. It becomes dangerous when a scalar raises its fins until they tear and stands sideways. Shortly afterwards, he charges at the intruder at high speed. Other fish but also the hand of the owner can be the target. Other angelfish are particularly badly attacked. In small and medium-sized aquariums, other angelfish are fought until they are gone.

Aggressive behavior with new scalars

If a new scalar or several new scalars are added to existing scalars, the previous division of territory of the long-established animals gets completely out of hand. Even if the animals sometimes move through the aquarium in groups, they demarcate areas that they defend. Especially during the spawning season or when they want to be left alone. The area sizes can differ depending on the pool setup and pool size.

New angelfish are alien in such a structure and must first find a place in the group. New angelfish are therefore often aggressive at the beginning and hunt the existing angelfish.

In favorable cases, this will subside after a few days. New animals are then integrated into the group and into the division of the territory.

It can also happen that the old, in turn, violently attack the newcomers.

Depending on how strong the mutual attacks are, animals must be removed from the aquarium. The basin size and the room layout in the basin are decisive. If the animals see each other all the time, this is in principle a stress factor that they reduce through aggressive behavior.

The integration can be accelerated somewhat by feeding. If live food is fed into the tank at different points at the same time, integration can be promoted. If that does not help, inferior animals must be constantly removed from the aquarium.

Last update on April 27th, 2021 / * Affiliate links / Images from the Amazon Product Advertising API