I assume this is in reference to your shrimp, and you floated him in the bag for 30 mins? If so, this is NOT the way to acclimate shrimp.
Salinity and Ph shifts are what do these little guys in. You have to drip acclimate them slowly over approx 2 hours for best results. Sure there are exceptions, and you could get lucky sometimes, but I find this personally a sure fire way for shrimp.