What is acclimation?
When we purchase a fish from a pet store, it is transported using water-filled plastic bag. Upon arrival to the target aquarium, an acclimation process is necessary to gradually change the water conditions inside the bag and the fish is released to its new habitat only when the conditions inside the bag are sufficiently close to that of the target aquarium. This process is necessary because aquatic animals, such as fishes or invertebrates, are extremely sensitive to the condition of their liquid environment; these include temperature, salinity, ph, and other chemical composition. A sudden change in any of these conditions results in shock which frequently produces disease or death to the animal. Therefore for long-term success it is necessary to acclimate the aquatic inhabitant to its new environment with as little trauma as possible.

The traditional method of acclimation for aquatic animals has been to float the plastic bag containing the animals at the aquarium, and manually adding a small amount of water to the bag at some fixed interval of time, say every 5 minutes. Due to thermal transmission through the bag, the water temperature inside the bag gradually changes toward that of the aquarium; also, the slow introduction of water to the bag produces gradual changes of water conditions. The process as described, however, is tedious and error-prone since the pet owner must supervise and manually execute the procedure for an extended period of time, typically more than twenty minutes. Moreover, water addition using a cup produces step changes in water conditions that is not ideal, since for the smoothest transition we want the water to be diluted on a drop-by-drop basis.
For more sensitive organisms such as shrimps, anemones, or corals, the dripping method is often recommended since water dilution is done on a drop-by-drop basis. In this method the entire content of the bag is poured into a container, and water from the aquarium is brought in using a hose and allowed to drip into the container. The drawbacks of this method are that the initial pouring into an empty container is highly stressful to the animal, and the amount of water inside the bag might not be sufficient to provide an adequate level in the container; furthermore, because the container is not submerged into the aquarium, the water temperature at the container and the water temperature at the aquarium might not equalize, due to the fact that the dilution process is slow and the room temperature might be very different to that of the aquarium.