When you hear somebody say that you must do this or that in order to keep your fish “happy,” or that your fish simply cannot be “happy” in that size tank, what do they really mean? Are they using the word “happy” in place of “healthy”? Or do they really mean to imply that true happiness can be identified and then quantified in fish? People must be mindful not to project human emotions to animals that do not have the capacity to feel them.
An animal rights advocate may look at a single fish in a tank and exclaim, “How unhappy that fish must be all alone in that small tank!” I suspect that in these cases, they do not mean the fish’s well-being and health, but that it is truly unhappy in the mammalian paradigm of how the word is generally used in English.
The following is my working definition of “appropriate aquarium husbandry,” and I say this equates to “happy” for a captive fish: If the fish shows no signs of chronic disease or abnormality, exhibits normal feeding and reproductive behaviors, and, most importantly, exhibits a normal life span compared to that of wild counterparts (minus the predation wild fish incur, of course), then there is no other metric we can use to determine if certain husbandry techniques are suitable or not.