1. BODY SHAPES: As mentioned earlier, male koi tend to have a slender body shape, while female koi have a rounder, fuller body shape. This difference is more pronounced as the fish mature and reach sexual maturity.

2. FINS: Male koi have longer and more pointed pectoral fins than females, which are often held erect during breeding season. In addition, males may develop longer and more pointed anal fins than females. Females, on the other hand, may have more rounded and shorter fins.

3. TUBERCLES: During breeding season, male koi may develop small white bumps, called tubercles, on their head or gill plates. These bumps are used to grip the female during spawning, and are a good indication that the fish is male.

4. VENT SHAPES: As mentioned earlier, the vent is the opening for waste elimination, and can be used to help identify the gender of koi. In females, the vent is round and typically located further away from the body. In males, the vent is oval or slightly concave, and located closer to the body. It may also protrude slightly during breeding season.

5. BEHAVIOR: During breeding season, male koi may become more aggressive and territorial, chasing and nudging females in an attempt to spawn. Females, on the other hand, may become more passive and avoid the male's advances.

Keep in mind that some koi varieties may have physical characteristics that make it harder to determine their gender, such as long fins in both males and females. Additionally, younger or smaller koi may not show obvious gender differences until they mature. With practice and experience, however, you can become better at identifying the gender of your koi.