How much temperature change are you getting in the pool? The built in Salt measurement systems are temperature sensative. If the temp has dropped a lot since you opened that may be why you have see the add salt message. My PPM has been reading between 2.5 and 2.8 since I openned the pool depending on temp. 2.5 at 55-60, 2.8 at 68-70. 2.5 is on the low end for my SWG system, but 2.8 is about right so I haven't added any salt yet.