Has Your Fish Outgrown Its Tank?


photo credit: reef2reef.com/forums

You may have been told that a fish will never outgrow its tank, and, while not true, this misinformation is perpetuated by fact. While technically an old wives tale, the truth is that most fish will die if kept in an undersized, overpopulated tank, but usually before they visibly outgrow it. With proper care for both the fish and their tank, though, early death can be avoided by giving fish enough space to reach full size and thrive.


The general rule for stocking fish is one gallon of water for each inch of fish. But while most fish owners do adhere to this rule, many think of the present, adolescent size of the fish when they purchase them, not considering how large their finned friends will be when they mature. A 20-gallon aquarium may seem well suited to four three-inch fish, but when they reach ten inches several months later, the tank becomes overcrowded.

Fish continue to grow their whole lives, but growth becomes minimal after reaching adulthood. Individual fish reach differing sizes, just as humans do, and their size is determined by genetics and influenced by volume and quality of diet, cleanliness, and available space, nutrients, and resources.

Placing or keeping fish in too small of a tank can result in weakness of skin and scales, skeletal deformities, repressed immune systems, suppressed appetite, and digestive problems due to the toxin levels in the water of a crowded  tank. Frequent outbreaks of disease are common in overpopulated tanks, because the fish are less able to resist pathogens. Poor water quality from overstocking can cause weakened kidneys, gills, heart, and liver because waste cannot be properly dispersed, and the fish takes it back in as he swims.

To avoid a crowded, overpopulated tank and unhealthy, dying fish, consider the full-grown size of your particular fish species when you buy them, and place them in the proper tank from the beginning. If you already own your fish, observe them carefully. If they start acting abnormally or becoming aggressive, you will need to provide them with a larger underwater haven.

PCH Tanks is available – day or night – to assist you in keeping your fish healthy and happy. If you have any questions or needs, feel free to call us at 949-933-8190. We specialize in Perfectly Clear and Happy Tanks!

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