directions on prime bottle:
Use 2 drops for each 4L (1 US gallon) of new water. This dose removes approximately 1mg/L ammonia, 4mg/L chloramine, or 5 mg/L chlorine. May be added to aquarium directly, but is better if added to new water first. If adding directly to aquarium, base does on aquarium volume.
Sulfur odor is normal. For exceptionally high chloramine concentrations, a double dose may be used safely. To detoxify nitrite in an emergency, up to 5 times normal dose may be used. if temperature is >30C (86F) and chlorine or ammonia levels are low, use a half dose.