yup, it should be fine, but the longer a fish stays in a bag, the more CO2 builds up and the lower the ph gets (check the pH the next time you have fish bagged for hours). at low pH, ammonia isn't very toxic ( there will be ammonia build up after a few hours). the danger is when you open the bag, the CO2 escapes, the O2 equalizes, the pH shoots up and the ammonia becomes toxic. (which is why you'll see some LFS's just dump new fish into the system). a little am-gaurd or other ammonia remover will do wonders to prevent ammo burn during acclimation of overnighted fish.