I acclimatize all my shrimps normally take only 15 minutes. If they are newly arrived shipments I stretch it to 30 mins. Normally it's ok to pour out 1/3 of the bag water, fill it up to the original amount with your tank water. Wait for some time that you are comfortable with, look if the shrimps are behaving normally. If they seem fine then repeat the process. After doing this for 3-4 times I just pour them into my tank already.