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Behavior of the fish

Behavior

Fishes behavior in an aquariumreflects their life style in a natural habitat, albeit modified by thefact that they are living in a more cramped environment, coming intocontact with other species more quickly and easily. Fish from the samespecies canbe have differently from one aquarium to another, accordingto the capacity and the other occupants.

• Territorial behavior

Whenfish are in their original biotope, their territorial behavior isreproduced in captivity, and issometimes even intensified. A territoryis a living space – either permanent ortemporary (as in thereproduction period) - with an extension proportional tothe size of thefish. Its occupant rebuffs individuals from the same species,fromrelated species, or even from totally different ones. The surfaceareamust be sufficient for the fish to find refuge, food stuffs, andfish of the opposite sex with which to reproduce. With some fish,particularly marine species, it is important to plan a territory in theaquarium that will provide shelters and hide aways.

• Group behavior

Strengthis to be found inunity, and living in a group permits a better defenseagainst enemies. Indeed,from a distance a group or school of fish takeson the appearance of a massthat is capable of surprising andintimidating an enemy. Group life also facilitatesreproduction, as anindividual has a greater chance of finding a fish of theopposite sex. Agroup's unity and organization are governedby a series of signalswhich are invisible to human eyes: the use of the lateral line, forexample, prevents fish from colliding with each other.

• Dominance behavior

Thebiggest members of aspecies dominate the smallest ones: when the latterget bigger they are ejectedfrom the territory. Dominance behavior haspractical and social implications,as the dominator will have priorityin food and the choice of a fish of the oppo site sex. At the bottom ofthe social ladder, the most dominated fish is permanently subject toaggression and harassment and has to hide most of the time, with itsgrowthbeing prejudiced as a result. This is the case with some speciesof AfricanCichlids.

• Prey-predator relationships

Somefish feed on other smaller ones in a natural habitat, giving rise to incompatibilities in an aquarium: take care, for example, not to letSouth American Cichlids cohabit with Characins.

• Aggression

Sometimesan aquarium is astage for aggression between different species. Thisaggression is alwaysjustified, as it is related to the defense ofterritory or offspring. It is aproblem of space – these phenomena arerarely seen in big aquariums. However, anew fish introduced into a tankwill often be considered as an intruder, orprey, and will be harassed.

Swimming

Behavior-of-fish

It is essentially the rearpart of the body, particularly the caudal fin, which serves to propel the fish,while the other fins play a stabilizing and steering role. Of course, the morehydrodynamic a fish's form, the more it is capable of setting off abruptly and swimming quickly, indispensable for catching prey or fleeing an enemy.
Aquarists are sometimesadvised not to let quick and lively fish (like Barbs) cohabit with slower andmore placid species (like loaches), as the latter may be frustrated in their attempts to eat the food provided by their owner.

Growthand longevity

Unlike human beings, fish continue to grow throughout their life, quickly at first, and then more slowly with age. The size of fish in aquariums is mostly smaller than that found inthe wild, undoubtedly as a result of the restricted living space at theirdisposal. This can easily be put to the test: an individual whose size has seemingly stabilized starts to grow if it is put into a bigger tank. As regards longevity, this varies according to the species: a year, more or less, for the small species, and two to five years for the majority of fish.Some patriarchs live to the ripe old age of ten or more - these are large fish,particularly marine species. It is very difficult to postulatean optimal life span for a given species in captivity, as environmental conditions introduce too many variable factors.