tanks are usually smaller tanks people keep to treat fish that become diseased. They take the sick fish from the main tank and move it to the QT
for treatment, also new fish are put into the QT
so that they can be acclimated, and be sure they are not diseased before they go into the main tank. Acclimation has to due with the process of introdicing fish into a new tank. There are several common practices. Some just float the bag (not recomeneded for salt), other use a drip method where people take an airline tube and put a not in it and start a syphon causing a drip the water and fish are placed in a bucket and the drip is done over a period of time sometimes and airstone is added to the bucket.