You often see it written that goldfish in a lake will grow really big but will not grow more than a few inches in size in a bowl or a tank. Likewise with sharks, which will remain very small in a tank.
This part is true.
Now here’s the motivational myth; the goldfish (or shark) doesn’t remain small because its dreams and horizons are limited. They probably wouldn’t grow much bigger in a bigger tank. And it’s not because they are no longer free to roam the lakes or seas.
It’s much simpler (and sadder) than either of those reasons. They are stunted (and sometimes deformed) because they are sick. They’re not growing properly because the water quality in most bowls and tanks is poor. It’s not changed often enough, because it probably doesn’t look dirty, but it’s probably full of various contaminants. The fish aren’t sick enough to die, but they’re not healthy enough to grow normally.
To reach their full potential, they need a healthy environment with good nutrition to keep them well and active.
And, yes, unless they’re really well fed, the sharks in an aquarium will eat the other fish (that’s another myth!).
So there is a genuine motivational message here, just not the one you usually hear. We all thrive in a nurturing environment, even sharks.
And, just as an extra thought, I came across this message several times whilst researching this article:
PLEASE DON’T KEEP GOLDFISH IN BOWLS. THANK YOU.