Sakana-kun, or ‘Fish Boy’, is a rising star on YouTube. He has built up a keen following among fish enthusiasts, who have been won over by his good-natured excitement about all things fishy.

Keen to share his love of fish, Fish Boy recently uploaded a short video in which he guides fans around his ‘Fish House’, the enormous aquarium he has built inside his home. The video is subtitled in English so it can be enjoyed by fish lovers overseas as well as in Japan.

As you can see, Fish House has a round window, which makes it look like a face. Apart from Fish House, Sakana-kun is also the proud owner of a six-ton fish tank. The temperature inside Fish House is kept at a steady 20 degrees centigrade, which is just right for his gyo-chan (‘fishy-wishies’).

Fish Boy likes to don his special fish hat whenever he goes into his fish house. ‘How many fish do you keep, Sakana-kun, that you need such a large amount of water?’ the interviewer asks him. “I have about 300 fish and about 80 types of fish,” he replies with boyish enthusiasm. “Many of them are rare and valuable species.”

Fish Boy might come across as a keen amateur, but he is in fact a true scholar when it comes to fish. He is an honorary doctor and a visiting associate professor.

Fish Boy says that he gets most of his fish from fishermen acquaintances, who make regular trips to the fishing grounds south and east of Tokyo.

He gets the water he uses in his tanks from the Tokyo University of Marine Science and Technology. It is specially sterilized and filtered seawater and is ideal for research purposes.

Sometimes, the fish arrive unwell, having either picked up an infection somewhere on the journey from sea to fish tank or been injured by the fishermen’s nets. Fish Boy prepares the appropriate medical treatment and takes care of the fish until they make a full recovery.

Fish Boy says that he can happily spend hours just watching fish slowly moving around. By observing them up close over a long period of time, he is able to understand their characters and temperaments, how they interact with one another, and the roles each of them plays.

He says there is still a great deal to be learned about fish. “They don’t fight. They’re surprisingly indifferent to each other,” he says admiringly.

Fish Boy particularly enjoys watching the mating process. He is currently immersed in a project to breed Ishigaki fugu – the notorious Japanese blowfish beloved of risk-taking diners - and is looking forward to the day when he’ll be able to watch the hatchlings grow.

Fish Boy’s YouTube channel is called ‘Sakana-kun Channel - FISH BOY.’ You can watch it https://www.youtube.com/channel/UCKUlE6-Ezy7CIe7PfKmIM5Q