Hello everyone. First off first post here. Trying to start a 40 gallon. Just doing it slowly. So I purchased a refractometer sight unseen and none refundable. Unfortunately I believe it isn't for saltwater. It says sodium chloride on the bottom, 20Degree Celsius at the top 0-25 scale on the right, and 0-30 with Saturation point on the right. Is it possible to use this or am I just out the money and need to get a new one? Thanks everyone!!