Greenbelt held a candidates' forum last week, at which five of six persons seeking a vacant council seat spoke to a packed meeting room.

The post became vacant last November when former Greenbelt mayor Richard Castaldi was elected to the County Council. He was succeeded by City Council member and Mayor Pro Tem Gil Weidenfeld.

The six candidates have long histories of service to the city, having served on different boards and in one case as mayor, council spokesman Gudrun Mills said.

The five candidates at the forum were:

* Ronald A. Ott, a member of the city's Park and Recreation Advisory Board.

* Robert C. Zugby, who serves on the Community Relations Advisory Board and the Crime Prevention Committee.

* Judith F. Davis, a member of the city's Advisory Planning Board.

* Antoinette M. Bram, a former member of the Park and Recreation Board and now a member of the Advisory Planning Board.

* Francis W. White, a former mayor and state delegate.

The sixth candidate, Joseph C. Isaacs, was not present, but his supporters presented statements and played a tape recording from him. Isaacs, a member of the Park and Recreation Advisory Board, had another engagement.

The council will discuss the choices in an executive work session Monday and will elect the new council member Jan. 24