While it would not harm the zoysiagrass to aerate annually, aeration is typically only necessary to correct lawn problems and not as a routine maintenance activity. Aeration is most beneficial in rejuvenating lawns that have become severely compacted through foot traffic, dog trails, etc. Aeration does, as its name suggests, allow the penetration of oxygen into the soil. Aeration is accomplished with a core aerator, a machine that physically removes cores from the ground and leaves hole. The proper time to aerate is after a good rain or thorough irrigation and when the grass is actively growing.