Just pulled this up on wikipedia. Cant believe it. Now if only your local lfs
did the same so new hobbyists had some knowledge.
The "inches to gallons" ethic may still be applicable for, say, ten 1-inch fishes in a ten-gallon aquarium, as their total biomass would occupy very little of the available square inches of space.
Similarly, if the number of fish an aquarium impedes free movement, or if territorial disputes frequently occur, growth will retard in response to the restrictive environment. In addition, increased susceptibility to disease or a disease-like state will be conferred upon cohabitants. In overpopulated tanks, it becomes difficult to maintain healthful water parameters; metabolic waste (excrement) accumulates rapidly, even when a highly efficient filter is employed. Frequent gravel vacuuming is required to keep nitrate and nitrite levels within acceptable parameters. Although bona fide infectious diseases such as Ichthyophthirius multifiliis (Ick) do not spontaneously appear due to overcrowding itself, a disease-state results from elevated nitrates. Fish will gasp at the surface in a futile attempt to absorb oxygen because the elevated nitrates block the metabolism of oxygen from the water i.e., the fish begin to suffocate. Also, in crowded aquariums, there is often an increased incidence of fin-nipping, which can lead to infection, decreased fitness, elevated stress and death.