When Pflugerville officials saw hydrilla and pondweed overtaking parts of Lake Pflugerville they called in the Moss Monster.

What may sound like the plot of a horror movie is actually a common occurrence in Central Texas' lakes.

The fast-growing aquatic plants can overcrowd a body of water, which hinders recreational activities and disrupts the ecosystem. Park and city officials fight back against the aquatic plants with mechanical trimmers and specialized fish.

For James Wills, Pflugerville Public Works Department director, keeping the plants in check while maintaining Lake Pflugerville's ecosystem and promoting lake recreation is a balancing act.

"It is a matter of us being proactive in what we see and what we do and just monitoring our water quality and monitoring the recreation side of it and working with the parks department," Wills said.

The city has contracted with brothers Jay and Clifton Chowning, owners of the Moss Monster, in an effort to trim back the hydrilla and American pondweed that have choked up portions of the lake during summer months.

The Moss Monster looks like a steel paddleboat mated with a giant underwater hedge trimmer and conveyor belt. The machine traversed Lake Pflugerville in September and October mowing down the aquatic plants 5 feet beneath the surface and depositing the cuttings on the bank for the city to haul away.

"The lake will look better, and [the cutting] will get the pond scum off the top and it will get the trash and cups and the stuff that blows in the lake," Jay Chowning said.

In addition to the mechanical trimming, Pflugerville officials have worked with the Texas Parks and Wildlife Department to introduce triploid grass carp, which are sterile, to the lake. The fish are native to Asia and eat hydrilla and pondweed.

Wills said the city had to obtain a permit to buy the sterilized carp and consulted with the parks department on the release of about 900 carp in 2011 and 2012.

Wills said the carp are not large enough to control the hydrilla and pondweed yet, but they will grow and hopefully help regulate the plants in years to come.

Because the carp can grow up to 60 pounds and live more than a decade, Wills said city officials were conservative in how many they released. Overloading the lake with carp could lead to excessive depletion of aquatic plants and diminished oxygen levels, which could result in killing fish native to the lake, Wills said.

"You have to be careful," Wills said. "You don't want to put too many carp in."

Controlling the weeds are, in part, meant to keep residents such as Michael Ledet coming back to Lake Pflugerville.

Ledet lives in Pflugerville and kite surfs at the lake. However, he said encroaching hydrilla makes it difficult. Kite surfers ride a board while tethered to a parachute-like kite that pulls them across the water.

Ledet equated kite surfing over the lake and hitting hydrilla to a cyclist unexpectedly hitting a patch of soft sand.

"When [the hydrilla] is up at the surface you can see it, but sometimes it is right beneath the surface and you can't see it. Then you'll just hit it, and you'll fall," Ledet said. "You'll go flying off your board."

Ledet said the lake became too overgrown with weeds this past summer, and it deterred him from kite surfing.

"They are going to have to come up with a plan if they don't want the lake to look like that every summer," Ledet said.

Wills said the city would continue to monitor the weed growth and use mechanical trimming. The city could also release more grass carp if the parks department recommends it.