Residents living near a Whidbey Island lake known for trout fishing are looking to a plant-eating fish for help in eliminating weeds choking the water.

This summer, Lone Lake became almost unfishable, unswimmable and unboatable as a non-native, invasive aquarium weed present in the lake for years almost grew to the surface in almost every area. At the same time, a late-summer bloom of what appeared to be a toxic algae bloom may have made the lake an outright hazard for human and animal lake users.

For the past several years, the residents around Lone Lake have been dealing with an infestation of Brazilian elodea, a submerged broadleaf that has spread throughout the lake. It gets into lakes when people dump their aquariums. Once in a lake, it can be spread between bodies of water by boaters or on fishing gear.

“The weeds are taking over the lake,” said Bill Russell, a homeowner near the lake who is also a member of the Lone Lake Homeowners Association.

Russell said the South American plant has eliminated most of the native plants in the shallow lake, which has a maximum depth of just over 20 feet. He believes fish in the lake are also threatened because the plant depletes the oxygen content of the water.

Fearing that the lakes status as a fly fishing trophy lake, as well as lakefront property values, could be affected by the infestation, the homeowners association is applying for up to $47,000 in state grant funding to pay to stock the lake with weed-eating carp. In addition, if the infestation is found to be bad enough, the association — with approval from the state — may use a water-bourne herbicide to kill off the Brazilian elodea.

The weed, which appeared in the lake in the mid 1990s, is commonly used in aquariums, said Susan Horton, coordinator for the Island County Weed Control Board. She said that the plant is highly aggressive and can change the dynamic of the lake.

After meeting with officials from the state’s Department of Ecology last month, the homeowners association learned that it could qualify for state grant funding to stock the lake with sterile carp and, if necessary, to pay for herbicides.

Pat Clark, president of the Lone Lake Homeowners Association, said while he is aware that either measure could upset some South Whidbey residents, the association cannot do nothing.

“We’re afraid if we don’t do anything, the lake is dying,” he said.

The carp are the preferred solution. Island County’s Horton said carp have a voracious appetite for elodea. Living up to 10 years, the sterilized fish will have some time to put a dent in the weed problem, though that may not be enough. Russell, who is writing the grant for the homeowners association, said if the elodea population is found to be too dense, it may need to be poisoned prior to the introduction of carp.

Before doing anything, the association needs permits from Washington State Department of Fish and Wildlife, the same agency that stocks the lake annually with trout. Russell said that state agency hasn’t made a decision on whether the homeowners can use the carp.

The state may require the homeowners association to develop a plan to manage the weed removal. That would mean that 2005 would be the first opportunity for treating the lake with carp or chemicals.

Because state grant money can only be distributed by a government agency, Horton asked the Board of Island County Commissioners this week to sponsor the grant. At their Monday meeting, the commissioners said they would consider the request.

Kathy Hamel, an aquatic plant specialist for the Washington Department of Ecology, said even if the homeowners group pulls together the money to stock the lake with carp, it will take constant work to keep the weeds at bay.

“Once a noxious weed gets into a lake, it is very difficult to eradicate it,” Hamel said in an e-mail this week.

In past years, the association has used an underwater weed mower to cut the top three feet of weeds off. This has been successful in opening the water for boaters and swimmers. Even so, there are plenty of weeds left: Russell said he has to clean broken weeds off his beach almost daily, even during the fall.

As for the algae bloom, Ecology’s Hamel said the microscopic plant is nearly impossible to remove from the lake. Fortunately, as the sun shines less during the winter, algae blooms typically break up and fade, along with the toxins they can carry.

Any weed eradication work would have to be done by a private contractor, as Ecology is not in the weed-killing business. Funding granted to the homeowners association would have to be matched at the rate of 25 percent.

Record editor Matt Johnson contributed to this article.