THE #1 MYTH IN FISH KEEPING

MY FISH WILL ONLY GROW TO THE SIZE OF IT'S TANK.

This has got to be the oldest and biggest myth still in the fish keeping hobby.  The size of your tank will not determine the size of your fish.  It is true that the growth of a fish can be stunted, but it's not the size of the tank that causes this to happen.  The water quality is the real cause, more specific, a high nitrate level.

Nitrates in high concentrations will stunt the growth of your fish over a period of time, but please don't use this to do such a thing.  If we consider the effects of this, stunting the growth of the fish is not the only harm the nitrate level causes.  Anything powerful enough to stunt growth and development must also be causing other damage, right?   

The stunting of growth is only the part we can see, visibly, at first.  This is the long road to death if allowed to continue uncorrected.  There is also the burning of the gills, skin/scale problems eventually develop, behavior changes, changes in eating habits, and other things that happen slowly.  As a fish experiences these problems to whatever degree, their immune system is also being weakened.  A weak immune system contributes to disease, and an inability to fight it.

When a fish outgrows it's environment, the ammonia output increases.  The bacteria break down the ammonia, the end result of which is a higher nitrate level.  If water exchanges are done properly, maintenance is increased, it is possible to have a 6 inch fish in a 10 inch tank, and still growing at a normal and healthy rate.  As long as that fish can move about properly to push water through the gills to obtain oxygen, this can continue, but the safest thing to do, and to alleviate the added maintenance and risk of "over cleaning" the tank, is to move the fish into the proper sized aquarium.  I wouldn't want to live in cramped quarters, even if it was clean... so I don't expect my fish to live that way either.  Mother Nature has her way of keeping things stable.  When we mess with Mother Nature we have to be prepared to compensate for the conditions we take away from these wonderful creatures.