The test is simple; estimate the time in seconds it takes the pool cleaners wheel to complete ten rotations (Use the yellow marker as reference). The right flow is when ten rotations take 20-26 seconds. Below 19 seconds means there is a problem with your Zodiac.
It may be possible damage but in most cases, decreasing the flow solves the problem. When it takes longer than 26 seconds, there might also be a problem and the culprit here again is the flow; increasing the flow works the magic.