Answer:

It is unlikely that the particulate is sodium chroride (salt) unless it has not yet dissolved. After it is dissolved it does not typically come out of solution. It is more likely that this is one of two things. 1) Algae - treat with an algaecide and vacuum the settled particulate to waste. 2) Calcium (hardness) - balance the pH and allow to equalize for at least one filter cycle. Then you may still need to add a clarifier to help clear the water. If the hardness is high, consider a partial drain and refill to lower the level.