Congrats on ur new fish. i would leave the new addition in qt for 1 day let him catch up with the new tank.
sometimes tangs can show small white pigments on the skin specially when they are mad or stressed. its not ick its a color changing pigments on their skin.
If thats what u observed which is very common in naso then ur good.
Any how i would give him 1 day and then start dropping salinity to hypo 1.009.
also if ur tank is not showing any signs of ammonia or nitrite then i would leave the media sponge filters etc in and not change them.
replacing them can or might through the tank in a mini cycle.
i personally never replace or clean or change out ceramic media ever. i never use sponge of filters either. if ceramic media (inside a media bag) looks dirty.... i shake them clean inside the tank when there is no fish in the tank. then do a 100% water change and be ready for round two.
My fish are great i completed 2 weeks of hypo today and i used prazipro and formalin ms all in conjunction for first time as an experiment. they all seem ok and eating and healthy.
i redid my 350gal tank and started the cycle. i am expecting the cycle to be over in next 10-14 days as i had the sump still running the frag tank and it has 2 yrs old 50 lbs rubble rock in it already.
ammonia was 2ppm yesterday today it was 1ppm. nitrites were 0.5 today 1.0 so i see there is bacterial activity already there. shouldnt be that long. once main is ready i will start bring the hypo back to match DT and once there i will transfer the non aggressive fish then few days later semi aggressive then last the tangs.