I'm posting the salt concentration table you asked for by PM on here because it won't fit in the space available for my answer.

With my usual caveat that I'm not in favour of adding salt to ponds as a permanent addition, itís an excellent medication as a short term dip, or as a medium term treatment in a quarantine/hospital tank or even as a very temporary addition in the pond itself to treat a diagnosed problem where salt is the recommended treatment. Therefore the students on my water quality course need to be able to calculate dosages for all circumstances where salt might be used so I calculated this for them to use whatever measuring system they prefer.