Gaithersburg city employes soon will have control over how their retirement funds are invested.

The City Council Monday authorized the retirement committee to devise a program that will give employes yearly investment options.

Under the present system, the city puts retirement money in a fund, which the Maryland National Bank invests in stocks, bonds and the money market, according to Gaithersburg Finance Director Roger L. Anderson.

"The bank invests about 27 percent of the fund into the money market and the remainder into stocks and bonds," he said. "This is good for the younger workers because stocks and bonds make money in the long run, but not so good for the veteran employes."

Anderson explained that older employes prefer the short-term returns paid by money market investments.

In 1980, $377,000 in retirement fund money was invested. This represented 8 percent of 68 employes' salaries.

In other business, the council authorized the city manager to contract material and labor for a fence at Rabbitt Park.

Long Fence Co. of Germantown will receive $8,399 for fencing in part of the park. Poolesville Trying ---To Control Crowding

The town of Poolesville wants to restrict homeowners from building too close to neighboring lots.

The town's Board of Commissioners Monday introduced a zoning amendment that would help control overcrowding in the community's subdivisions, according to Commission President Charles Elgin Sr. The amendment would restrict residents from building less than 30 feet from their rear-lot boundaries.

Under current zoning law, a homeowner can build as close as 10 feet from a neighbor's property.

The town plans to revamp its zoning codes but Elgin said the amendment is necessary now as a "stop-gap measure." The community's planning board, which recommended the change, has received several applications for enlarging homes, he said.

The town has scheduled a Dec. 21 public hearing on the amendments. Glen Echo Gets -----Housing Complaint --

The Glen Echo Town Council is considering action to eliminate multifamily occupation of homes in areas zoned for single-family dwellings.

The legislation was spurred by a resident's complaint that more than one unrelated family was living in one home, according to Councilwoman Deborah M. Beers.

Last week the council discussed different legislative alternatives, including a rental home licensing procedure, Beers said.

The council will take up the issue again at its next meeting, she said.