The Fun & Fitness Exercise & Aquatic Centers, which have operated in the Washington area for more than two decades, closed their doors quietly yesterday, stranding thousands of customers and a number of employes.

Consumer officials in Prince George's County, where two of the centers are located, and in Northern Virginia, where there are four, said they have been flooded with calls from members who went to swim or work out in club facilities and found them shut.

There was no immediate explanation for the closing, according to Jean Galloway, director of the Arlington office of consumer affairs, and William R. Bailey, acting director of the Prince George's County Consumer Protection Division. They said they had been unable to reach anyone with Beachwood Spas International, a Cleveland firm that had been operating the centers, or with the local club management office, which has headquarters in Fairfax County.

When officials checked to find out if Beachwood had posted the $50,000 bonds that are required as protection for consumers, they found that the company had only partly complied with state laws. Both Maryland and Virginia require that a bond, letter of credit or cash up to $50,000 be posted for each center. But Beachwood filed only one letter of credit in Prince George's County, where it has two centers, and only one letter of credit in Virginia, where it has four centers.

Galloway said that the company had reached an agreement on Dec. 1 with the Commonwealth of Virginia to post letters of credit or bonds for its other three locations by July 1.

Employes interviewed yesterday at the Arlington center said they had not been paid for the past month. Manager Carson Carroll estimated that the Arlington center, which opened in 1958, had more than 2,000 members and about 45 employes.

It wasn't clear when the clubs stopped selling memberships, but Carroll indicated that there had been sales as recently as last week. New members were charged $795 for the first 30 months, renewable at $92.50 annually, he said.

Bill Sennett, an Arlington insurance claims adjuster, said he paid $850 in January 1980 for his three-year membership, renewable at $50 a year. Sennett, who paid his $50 renewal fee a month ago, went swimming at the Arlington center on Wednesday night and found everything "normal." When he called yesterday with a question, there was no answer. "I called another center and the manager there told me they were closed," Sennett said.

The Fun & Fitness closings are the latest in a series of health spa closings here in recent years. Thousands of consumers have lost more than $1 million in memberships that they bought in clubs that folded, according to consumer officials.

The trend led to the passage of laws in both Maryland and Virginia requiring that fitness clubs post bonds that could be used to reimburse consumers who lost money in the closings.

The Virginia House of Delegates yesterday approved a bill that would require that fees collected before a spa opens be put into an escrow account and impose stricter registration requirements on all spas.

The bill, passed with little comment on the floor, also would revise a law approved last year that requires each spa location to put up a $50,000 bond.