The museum at Tokai University has bred 11 of the 28 kinds of clown anemone fish that originally came from the coral reefs of Australia, Japan's Kyodo news agency reported Wednesday.
The university hopes people who want the fish for their aquariums will buy them from the science museum rather than taking them from the waters off Japan.
It is the first time in Japan that an aquarium has attempted to sell ornamental fish.
If buyers are unable to care for the clown fish, the museum has offered to take them back.
Genjiro Nishi, who heads the science museum, warns buyers not to release aquarium-bred fish into the wild.