Sounds like the salt has not fully dissolved, which is definitely strange after 4 days. Did you stir the salt really well after putting it in the tank? Is there any salt on the bottom of the tank? Do you have a heater in there to aid in the dissolving of the salt?
An AC200 isn't going push the water around enough to be very effective at helping dissolve the salt. I think you need a higher water turn over rate than an AC200 does, especially over the long term.
Also, salinity should be 1.024-1.026.
HTH
