They are yet to graduate from primary school but the grade five and six students at Belgian Gardens State School know a lot about commerce and conservation.

"Every fourth clownfish we sell we will get enough money to feed all the fish in Reef BG (Belgian Gardens) for a month," grade six student Amalia Clarke said.

"Every one that we sell means one less clownfish is taken from the reef," fellow grade sixer Tanika Grevelle said.

The Townsville school started unintentionally breeding clownfish 10 years ago and now has 20 tanks, which are maintained by a team of 103 student volunteers.

Science teacher Brett Murphy said the Reef BG room teaches maths, science and conservation in a practical way.

"Because we live at the catchment of the Great Barrier Reef we can give hands-on real life learning for students," he said.

"Instead of looking at a book or watching a video we can give them the real thing," he said.

The school has been supplying local pet stores with clownfish hatchlings in exchange for fish food and aquarium supplies.

This month the program's reach extends nationwide, with the students' fish headed for a wholesale aquarium in Cairns, which supplies shops around Australia.

"That's a good learning experience for our students, as well to show that what we can do even in our little school, can have a greater impact on the rest of our society," Mr Murphy said.

Breeding 'Dory' a way off yet

Since the release of the movie Finding Nemo, clownfish have gained popularity as an aquarium pet, Mr Murphy said many were still taken from the wild.

"It is reported that about one million clownfish are taken from the reef each year," he said.

Mr Murphy suspected that the release of the Finding Dory film would generate interest in the Paracanthurus (blue tang), but said the school would not change their breeding program from clownfish any time soon.

"I don't think there is anyone in the world that has actually [captive] bred the blue tang, just because of the way they lay their eggs," Mr Murphy said.

"In the future if they were to crack that it would be a fantastic process us for us to be involved in," he said.