Anger not your fish.
Your fish are probably pissed off if you keep them in a small aquarium, suggests a study published this month
in the Journal of Applied Animal Welfare Science that looked at levels of aggression in the common aquarium species Midas cichlid
(Amphilophus citrinellus). Fish stored in average-sized aquariums used by most small collectors (i.e. tanks holding fewer than 100 gallons) were significantly more aggressive and violent than fish in artificial stream environments or home in their natural habitat. With 180 million or so ornamental fish in America, that's a lot of mad fish. Though the results may sound like common sense—no animal likes being housed in cramped conditions—this is one of the first studies to concretely measure aggressive bouts, attacks, and other behaviors indicative of the creatures' state of mind in aquariums of varying size and complexity. These bouts ranged from fin-flaring to nips and full-fledged ...
