Most bags of shipped fish the ph can get very low ,ive seen the bags at 5.0 and lower.Amonia is less toxic in a lower ph and the affects of amonia will take alot longer to affect the ray,PH shock can do more damage to a ray long term than short term.
Thats why you remove most of the bags water and keep just enough to cover the ray,use a fast drip line {do not crimp it,and let it flow open}with in 15 min you have replaced most of the water in the acclimating container with the tank water,then remove it to just above the ray again and let it flow for another 15 min.
And good to go,no need for detoxifiers or salt or stress coat.Net the ray and put in ,and he will be relaxed and ready to eat very quickly.
I have used this method for the last 17 yrs on everything from Cardinal tetra's to Discus and even salt water fish,with out any problems.