A skimmer will not clear the water. Could be cloudy from the salt mix, or, from stiring sand when adding the water.
P.S. Get a skimmer... A big one... With that many fish in the tank and aggresive at that, your playing with matches not having one.
A skimmer removes disolved organics, proteins, crap... Without one, they build up inside the tank and are only removed via water changes. Unless you want to do weekly changes, adding a skimmer will help remove these thus, decreasing a chance for them to buid up.
A skimmer can also help reduce nitrates by limiting their food supply.