[pogodzib]

If he was eating for a few days after you got your salinity lowered, but he has stopped eating now, I'd run some tests on the water quality. Lowering the salinity significantly, even in a tank that has been set up for a while, can kill off some bacteria and cause ammonia or nitrite spikes. I like to do a 10-20% water change 3-5 days after my salinity has been lowered.

If your water tests out fine, I'd start by trying to feed frozen foods soaked in a garlic additive.