Acclimating your shipped fish or invertebrates to their new tank
There are scads of articles, posts, and opinions on what the proper means of acclimation for a new fish or invertebrate are, and why they do or do not work. I am simply giving my opinion, based on what has worked for me, and the steep learning curve I have had since I started importing. My choices for acclimation are based on comparative observations I did on the survival rate of thousands of fish and invertebrates, they are by no means the ONLY way to do things.
Most books or resources in the past suggest floating the shipping bag in order to adjust the temperature. Despite it sounding reasonable, there are a few flaws to this logic. In reality, the cooler water of the shipping bag has caused the metabolism of the fish to slow and they have gradually adapted to the conditions of the bag during their shipment (usually 24-36 hours). By increasing the temperature so quickly their metabolism increases quickly and often they are hypersensitive to light and movement. When the temperatures rise, the available dissolved oxygen decreases which means as they are overreacting in the bag, they begin to suffocate. Secondly, as the shipping water becomes polluted during the trip, there is an excess of carbon dioxide produced which drives down the pH of the bag water. This effectively makes the ammonium produced much less toxic because of the formation of carbolic acid. Once the bag is opened, co2 is gassed off quickly causing the pH to increase quickly, converting ammonium to ammonia, and essentially burning the gills, skin, and fins of the fish. The increased temperature only increases the rate at which this occurs.
The following is the method which has yielded the highest survival rates for my purposes. First have a net, water conditioner, a container (bucket or pitcher), and some airline available. Immediately upon opening the shipping bag, add a few drops of water conditioner to detoxify the ammonia. Which product is not important, though I use Prime. From this point on it is preference. I prefer to then pour the fish into a net (over the bucket as they are quite jumpy) and add them directly to a dark tank. Typically they are adjusted and acting relatively normally, sometimes even willing to feed, within about 20 minutes. Many prefer the drip method. I have no issue with the drip method, but in order for it to really be effective, it should be done over a minimum of several hours.
To drip acclimate, simply add the fish to the holding container with enough shipping water to cover it (be sure you added the dechlorinator/ammonia binder). Then take your airline and start a siphon from your quarantine tank. Next you tie a knot (or use a two-way adjustable air valve) in the airline to provide a slow drip into the holding container. This allows for gradual increase of temperature, and a more gradual change of total dissolved solids.
From my experience, most hobbyists do not take enough time for drip acclimation to be less stressful than just adding the fish directly to the tank which is why I counsel to just add them quickly.