Cramped, Boring Environments Lead to Anger in Fish

You probably already know that if your aquarium environment does not live up to the standards of your fish they are unlikely to thrive. You may be surprised to learn, however, that an environment that is too cramped or dull can actually cause your fish to become angry. A recent study conducted by Case Western Reserve University shows that ornamental fishes kept in aquariums that are too small or improperly maintained are at a higher risk for becoming aggressive. If you think your tetras are giving you an angry glare, you may not be paranoid after all!

Laws Regarding Animal Cruelty

Ronald Oldfield, biology professor at Case Western Reserve University, writes that “the welfare of aquarium fishes may not seem important, but with that many of them [over 180 million] in captivity, they become a big deal.” While the United States and many other countries have laws regarding cruelty toward animals, those laws generally do not apply to aquarium fish. There are a few cases, however, where specific laws have been passed to reduce cruelty to fish. England, for example, prohibits the use of fish as prizes at fairs due to the intense heat and stress caused by being kept in plastic bags. In Switzerland, laws go even further to protect goldfish from physical and psychological abuse, decreeing that aquariums must have one opaque side so the goldfish can experience natural day/night cycles.

Though some laws have been passed regarding cruelty to aquarium fish, Oldfield is the first to conduct a large-scale scientific study on the matter. The results of his study are published in the online Journal of Applied Animal Welfare Science, volume 14, issue 4. The main subjects of the study were Midas cichlids (Amphilophus citrinellus). These fish were kept and observed in a variety of habitats including their native habitat in a crater lake in Nicaragua. Other habitats included an artificial stream in a zoo and small glass aquariums like those the typical aquarium hobbyist might use.

Details and Results of Oldfield’s Study

The size of the environment was the main factor being studied in relation to aggressive behavior in juveniles of the species, but other factors came into play as well. Oldfield also tested the complexity of the environment as well as the effect of different numbers of fish in the tank on fish behavior. Resources including food and shelter were removed from the tanks prior to observation so that direct competition would not affect the results of the study. To clarify, some of the behaviors Oldfield identified as aggressive include: flaring fins, nipping, chasing and charging at other fish.

The results of Oldfield’s study were very interesting. As was expected, of course, the size of the environment had a direct impact on displays of aggression. What was interesting, however, was the fact that the complexity of the environment also played a significant role. Tanks without hiding places and large decorations to break up sight lines resulted in more frequent displays of aggression. The closer the environment was in terms of size and complexity, the fewer displays of aggression Oldfield observed. This is an important tip for aquarium hobbyists to keep in mind when setting up their own aquariums at home.

Utilizing the Results of the Study

Based on the results of Oldfield’s study, it should be clear to you that the size and complexity of your home aquarium environment is very important for the health of your fish. If your aquarium is too small or if it is overcrowded to the point that your fish do not have adequate space, it could become a serious problem. The problem may start with aggressive behaviors in your fish but it could escalate to a much larger issue. Along with aggressive behavior comes increased stress levels and an increased likelihood for injury. If your fish are stressed or injured, they are also more susceptible to contracting disease. For the general wellbeing of your fish, it is essential that you provide adequate space and enough hiding places in the tank. The more your tank environment simulates the natural environment of your fish, the better off your fish are going to be.

Take a page from Oldfield’s book and do not overlook the basic needs of your aquarium fish. Even though they may not be able to interact with you as much as cats or dogs, aquarium fish are still companion pets that rely on their owners for adequate care. It is your responsibility to provide your fish with a suitable living space where they can be healthy and safe.