Immediatly do a 50% water change if it is 2ppm or below, make sure to match temp and all, if it is 4ppm or more do a more aggressive 60-75%. What is the exact reading, and what type of test? What brand? Strips or liquid? If you have prime, do a double dose after the water change if it gets below 1ppm.Right it’s definitely ammonia what’s the next step?