An odor reducing assembly for use in a marine vessel or RV waste holding tank including an aeration tube and an aeration pump. The aeration tube is disposed in a bottom portion of the holding tank. The aeration tube may be provided by a separate aeration tube or may be incorporated into the macerator/discharge pump. The aeration pump is in fluid communication with the aeration tube and supplies pressurized air to the aeration tube during operation of the marine vessel or RV. The aeration tube is disposed in a bottom-most portion of the holding tank and is submerged in sewage. Pressurized air from the aeration pump is injected into the sewage via the aeration tube and creates an oxygen-enriched aerobic environment therein. Air from the holding tank is continuously vented to atmosphere during operation of the aeration pump via a vent in the tank.