What kind of relationships do you think arise between the living organisms of the lake?

Once in the circus I saw a huge hippopotamus, he was so well-groomed. I always thought they were dirty because they lived in the lake. I asked the trainer: “Is the hippopotamus as well-groomed as yours in nature?” “Of course,” he replied. “After all, in wildlife they also take care of him – the fish are black labeo, they clean his skin, remove algae, old pieces of skin, various parasites and other debris. They clean his teeth and gums well, this relationship is also called symbiosis.” I saw that my father was going fishing: “What other relationships are possible between living organisms in the lake?” I asked him. To which the father said: “In our lake there are: bream, perch, crucian carp, chebak, ruffs, pike, catfish. Here between them there is food competition, that is, the struggle for food, and cannibalism is eating their own kind.”
As a result, I learned that the relationship in the lake between living organisms can be in the form of symbiosis, in the form of a struggle for food and cannibalism.