Your SG needs to be 1.025-1.026 anything less will stress your inverts causing premature death.
Just use a power head to mix your new saltwater for 24hrs before you add it to your tank, no air pump needed.
Cutting the lights will not fix the hair algae problem, it only delays the problem unless you fix the excess nutrient problem the hair algae will return as soon as your return to your normal lighting schedule.