More than 1400 students from early childhood to grade 12 entered this year's competition, with work centred on the theme Australian Science through the Ages.

Burnie High School grade 8 student Liam Grieve received the Liana Colvill Memorial Award, given to the most promising young scientist, at the University of Tasmania's Newnham campus.

The 14-year-old aspiring research scientist focused on preventing algal blooms in farm waterways with an experiment using native plants.

"I simulated a wetlands environment, poured a mixture of fertiliser, cow dung and manure and let water gush into the catchment container," Liam said.

He found that belts of planted grasses absorbed excess nutrients that could have caused algal blooms - an outcome that supported his hypothesis.

Tasmanian Science Talent Search director Margaret Hosford said Liam's work was chosen for the "careful, exact way he set it up".

It is the last year in which Ms Hosford will direct the competition after about 15 combined years of involvement.

"It's been enjoyable seeing kids year after year and seeing the teachers develop," she said.