The trip home
Make the shop your last stop. A paper bag or an insulated cooler keeps the bag dark, which calms the fish, and keeps the temperature steady in hot or cold weather. Keep the bag upright and out of direct sun and car vents.
Matching the temperature
Fish adjust to changes in temperature and water quality only gradually. Turn the tank light off and float the sealed bag on the surface for 15 to 20 minutes, until the water inside feels the same as the tank.
Adjusting them to your water
Open the bag, roll the top down so it floats, and add about half a cup of tank water every five minutes for half an hour. For shrimp and sensitive fish, drip acclimate instead: run airline tubing from the tank into a bucket holding the animals, with a knot or a valve to slow it to a drip or two a second, until the water in the bucket has at least doubled.
Fish that have been in a bag for many hours, such as fish shipped by mail, are the exception. Ammonia builds up in the bag, and the water becomes more acid as the fish breathe, which keeps most of the ammonia in its safer form. Opening the bag lets the pH climb and turns that ammonia toxic, so after a long shipment keep this step short. Why pH changes ammonia
Into the tank
Net the fish out of the bag into the tank and throw the bag water away, so whatever is in the shop’s water stays out of your tank. Leave the lights off for a few hours and feed lightly the next day. Add a few fish at a time and test ammonia and nitrite over the following days, since the filter needs time to catch up with the extra waste. A quarantine tank first is safer for your other fish. Quarantine tank setup · Check the new fish fit