The Civil Service Board shall formulate rules and regulations governing the selection, promotion and discipline of members of the Fire Department which rules shall, to the extent deemed feasible by said Board, be consistent with such rules of the other two Civil Service Boards and shall be enforced consistently as to all members, officers and personnel of the Fire Department. The Council may recommend amendment or repeal of existing rules and adoption of new rules to said Board. All officers shall belong to the classified service and shall be appointed and promoted for no other grounds and for no other reason than their fitness for the position to be filled: provided, however, that no member of the Fire Department shall be eligible for promotion until he shall have served at least three years in such Department and that in subsequent promotions the member must have held the rank from which he is promoted at least one (1) year. Promotions shall be made only to the next higher grade in the service and no grade shall be skipped; provided, however, that any member of the Fire Department, who has served not less than three years in such Department, may be appointed Assistant Fire Chief, Deputy Fire Chief and Fire Chief of the Fire Department. All officers or members shall be chosen or promoted by the City Manager, or designee, whenever a list of eligibles shall be furnished to the Civil Service Board, from the three (3) highest standing candidates on the list. (Amended March 26, 1996: amended June 2, 1992: amended November 8, 1988)