KANE'OHE — An underwater vacuum is rescuing the reefs in Kane'ohe Bay and providing valuable fertilizer for taro farmers.

Dubbed the "super sucker," the alien algae removal machine demonstrated its abilities yesterday at the pier opposite Coconut Island.

Divers grab alien algae and place it in a 4-inch diameter hose that sucks up the algae along with some 200 to 300 gallons of water per minute. All of this is spewed onto a screening bed that allows the water to drain while people check the material for sea animals or native plants, which are returned to the ocean.

Operators are careful to use the machine in a way that native species go unharmed, said Eric Conklin, a University of Hawai'i graduate student and diver in the pilot project. The removal of the alien algae has a dramatic effect on the coral, he said.

"The reef coral that was smothered and dying can return to health," Conklin said before going into the water. "Puka in the reef that were filled in by alien algae are cleared and can serve as fish shelter again."

Initial tests show the super sucker can remove up to 800 pounds of algae an hour. In terms of removing the stuff manually, which has been an ongoing effort for three years, it would take 150 volunteers and 10 divers to do the same work in an hour.

The machine is a modified gold dredger that has been fitted with a 40-horsepower diesel engine and runs on biodiesel fuel. It has no fans or blades, which means it won't inadvertently return algae to the water or cut it into small pieces that can easily reproduce.

The super sucker operates from a 13-foot by 25-foot covered barge that is docked at the Hawai'i Institute of Marine Biology at Coconut Island. It has a five-man crew, including two divers. The algae is packed into sacks and delivered to taro farmers who say it is a superior fertilizer, said Bryan Parscal, operations supervisor for the project.

So far about $500,000 has been spent on the project in the past four years.

Cynthia Hunter, with the UH biology program, said the alien algae was introduced in Kane'ohe Bay and Waikiki during research projects to create aquaculture in Hawai'i.

Some seaweeds are processed into agar — used in laboratories to grow bacteria and in food production as a thickening agent — and carrageenan, widely used as a gelling agent and to make ice cream and frozen yogurt smoother.

But the project didn't work out and the algae was abandoned. Several years later it started to grow at a rate of 250 to 300 meters a year.

By the 1980s UH research students began documenting the growth, and three years ago volunteers started to remove it from Waikiki.

The "super sucker," developed by Eric Co of The Nature Conservancy, was the brainchild of personnel from the state Department of Land and Natural Resources, and botany and biology researchers.

Co said research and development took about four years. The machine has proven to rid the coral reefs of well-established algae and can be used to prevent colonization.

"The super sucker was specifically designed to fit within a greater initiative ... to address the threat of invasive marine algae through education and outreach as well as continued manual removal efforts with community members," Co said.

The machine costs about $150,000 to operate a year, and has removed 25,000 pounds in the 12 months since it began operation, Parscal said.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.