Some fish, like the cleaner wrasse, provide cleaning services to other fish by removing parasites.

The mola mola, or ocean sunfish, is the heaviest bony fish, weighing up to 5,000 pounds.

Fish have excellent senses of smell and taste.

Some fish, like the flounder, undergo metamorphosis and change their body shape.

Fish scales can provide insight into the fish's age and growth rate.

The discus fish cares for its young by secreting a mucus coating that the fry feed on.

Fish play a crucial role in the food chain, serving as both predators and prey.

Some fish, like the goby, can live in extreme environments, such as hot springs and deep-sea vents.

Fish can suffer from diseases, including fungal, bacterial, and parasitic infections.

The fish heart has two chambers: an atrium and a ventricle.