Correct, and what you are seeing is known as associative conditioning. The fish see their owner approaching the tank, picking up various containers, in various shapes & colors, lifting the lid, and they have come to expect that the next thing that will take place is that food will be dropped in the tank. The food typically appeals to their olfactory senses, as well as their taste buds, and they eat.
Some people might see the above scene as illustrating a group of happy fish. I see it as a group of fish that are doing what comes natural to them. The fact that some fish prefer some foods over others, doesn't tell us anything beyond what we have always known, animals have preferences, sometimes for a multitude of reasons.
But the question then becomes should we ignore the nutritional value of foods based on human emotions, or feed what we know is best for the animal?
Offer a group of young children two platters of food; one platter filled with cake & candy, and another with baked salmon & steamed broccoli, and it should become crystal clear why it's up to us to choose what's best for our fish to eat. I'm certain that everyone will agree that cichlids do not have the same intelligence level as human children.
I agree that cichlids are very unlikely to have the same intelligence as human children, though regarding some adults I know, hmmm, i'm on the fence with that one
