The Rotonda condominiums in McLean would have amenities "equalled by few other communities in the world," promised a 1979 sales brochure of Giueseppe Cecchi's International Developers Inc., creator of the Watergate complex and other condominium projects around the Beltway.

A "spectacular view," IDI said, would look down upon a shimmering blue lake, for those willing to spend up to $130,000 for a condominium at the Rotonda.

But now, years after they put down their money and legally released IDI from responsibility for the development, residents find themselves spending their condo fees waging chemical warfare against a host of primitive, but prolific, life forms.

The tennis courts and landscaped greens end where the sales pamphlets showed they would, but steep banks slope downward from there to a shallow pool where a boundless crop of cattails, swarms of mosquitoes and what residents call "the green slime" flourish.

"It looks better than it has ever looked," said one condo owner of the pond's recent liberation from an algae growth that carpeted its surface. "And it looks horrible."

Cecchi noted that, aside from whatever the complainants believe his sales pamphlet depicted, the actual body of water was there for buyers to see when they first came to look at the condominiums. He said he promised nothing more than was delivered. "There was no suprise," he said.

Residents could rid themselves of the growths by raising the water level, but that is up to them, according to Cecchi. "They can do what they want," he said. "It's their property."

Actually, a solution would involve a bit more than adding water, according to William W. Smith Jr., assistant chief of Fairfax County'ss site review branch in the Department of Environmental Management.

To make a real lake out of the 148,000-square-foot wetland would require draining it and then dredging the bottom, Smith said. Before they refilled it to a higher level, they also would have to extend the height of a central drain that currently keeps the water level shallow, he added.

Smith inspected the "lake" last year at the owners' request. Smith said the body of water meets all the requirements of a "water retention facility," which is essentially a collecting pool that Fairfax requires developers to include in their designs as a means of controlling the rate of water flowing into the county's storm drains.

There are other ways builders can meet the "water retention facility" requirement. Smith said many install huge underground collection tanks in their drain systems, rather than have an open pond, because of the potential for growth of cattails and algae.

"The designer of the Rotonda had the idea that this would be a scenic amenity, or whatever," Smith said. "I guess beauty is in the eye of the beholder. I guess a fish and wildlife man might be content to see it. He might see it as the beginning of the food chain."

Cecchi said, "What we did was, instead of a water retention facility, we tried to make a facility out of it, a pond. We put a gazebo on it and tried to make it look nice.

"I can guarantee you, if Rotonda owners had any other expectation, I would have heard," he said. "When condominium owners get upset, the first one to hear about it is the developer."

Richard K. Grizzard, a business associate of Cecchi's and vice president of the IDI subsidiary that developed the Rotonda, went to look at the lake after one owner complained in May 1982.

"I find no problem with the overall general appearance, except that some might find the cattails not to their particular tastes," Grizzard wrote in response to the complaint.

Owners who were upset said they did complain to management companies and to the Rotonda Home Owners Association, but were told that the county required the water level to be kept low for drainage collection. By the time they had discovered that alterations could have been made to deepen the lake, a former owners association president had signed a bond that essentially was a legal acceptance of the project from IDI by the homeowners.

Owners who are still simmering from what they feel is a difference between what they were promised and what they got asked for anonymity. They still have to work with the other owners, who might not appreciate any controversy, they said.

Those residents said that there are several reasons why Rotonda owners don't complain publicly: Most live in buildings where they cannot see the lake; others bought units later and did not see the original sales brochures and slide shows; many residents are renters; and some who do have to live close to the pond either don't want to lower the value of their unit with publicity about the pond, or are resigned to living with it.

On a recent evening, John G. Muireid, ,chairman of the landscape committee of the Rotonda Condominium Unit Owners Association, stood on the concrete slab gazebo floor, gazing over the pond and puffing on his pipe.

Aside from his expected duties caring for opulent rose gardens and floral spreads around the majestic complex, Muireid had taken it upon himself to liberate the pond from marsh-dwelling vegetation.

He personally coordinated crews that applied chemicals and hacked away at the cattails.

This season, after three assaults of chemical spraying, the water surface became visible for the first time in months, Muireid noted with satisfaction. The green, clumpy growth had receded to the water's edges.

But drains leading to the pond still carry detergents and engine oil down from the parking lots, as well as overflow from the swimming pool, Muireid said. "I don't think it will ever be a lake like a lake is supposed to be," he said.