When I was but a young lad many seasons ago, I won a large number of goldfish at the New York state fair. This did not involve card games or dart throwing, but instead a large table filled with your vintage style fish bowls. Some of the bowls had goldfish, and if the lucky contestant could land a ball in the bowl with a fish, then he won that fish. Well, lady luck had her hand on my shoulder that day, because I won 40 goldfish (and my luck as deteriorated ever since).
Needing somewhere to store all of these fish, I obtained a tropical fish tank and some tropical fish to go with it. I am no scientist or biologist, but the goldfish were kept in warm, tropical water, and I am not sure this is the natural environment for a goldfish. Well, one of my goldfish flourished in this environ, and he grew very large. One by one, he began to eat ate all of the other fish, including my beautiful angelfish. He ate everything except for the catfish and the algae eaters, probably because even the great conquerers respect the maintenance people that keep everything clean. Still, I lost many fish to that beast of fin and war, and it taught me a lesson.
Don't take carp from anyone.