To add fish or invertebrates to an aquarium, you must introduce them to their new environment gradually. This is because the parameters of the water they are transported in vs. the parameters of your aquarium will likely differ. If you bring home your livestock and simply cut them loose into the aquarium, this can increase their stress and sometimes shock and kill them. Not to mention you can introduce pathogens into your tank from the foreign water source. Remember, if you already have an established aquarium, you’ll want to quarantine new fish before adding them to your main tank (see The Importance of Having a Quarantine Aquarium). There are two tried and true methods to get the livestock adjusted to your tank.
Most pet stores will recommend the floating method of acclimation. There are some variations in terms of how long to float, when to add water, etc. Generally, for this method you’ll want to float the bag in which the livestock was transported in the aquarium or quarantine tank for at least 15 minutes to get the temperatures equal. Make sure the lights are out on the aquarium to keep from heating up the bag unnecessarily during this process and to calm the animal(s). If you received your livestock in a breather bag, you will not be able to simply float it. In that case, either try the next method (drip acclimation), or cut the livestock into a container to float in the tank, such as a clean 32 oz deli cup. Once the temperature in the container or bag is the same as the temperature in the aquarium, cut open the bag or tip the container to allow some water from the tank inside. Wait another ten minutes, then repeat adding water, being careful not to pour the transport water into the aquarium. Generally, after 45 minutes to an hour have passed, it is considered safe to net the livestock into the aquarium and discard the water in the container.
Perhaps the most gentle method of acclimation, the drip method, allows you to control the rate at which you introduce aquarium water to your new fish. This will require a bucket and a drip line with a control valve. The first step is to cut the bag of water into a clean aquarium-use-only bucket. You may need to tilt the bucket slightly if there isn’t much water in the bag. If the fish have traveled for more than a few hours in the bag before getting to you, you will next want to add a drop or two of prime to help neutralize ammonia. Then, you place the elbow of the drip line over the rim of the tank to hold in place, letting the end with the control valve hang over the bucket. You may want a clip to keep this end positioned in the bucket as well. Essentially, you will be starting a siphon to get the drip line going. Remove the control valve, and use a small syringe to start the siphon. You can also use your mouth and suck on the end of it to get things going. This is not advised, however, due to germs in the tank. Once water is flowing, put the control valve back in place and adjust it so that it is dripping approximately 5 drops per second. After the volume of water in the bucket has doubled, it is usually safe to net the livestock into the tank. In the case of a dramatic change of parameters such as pH (you can test this beforehand), you may wish to drip for longer (up to an hour).
Proper acclimation of new livestock is paramount to success with aquariums. It is a vital first step to keeping fish and invertebrates safe. Once careful acclimation takes place, one can move forward with monitoring and quarantining livestock. If this process is rushed, it may cause undue stress on the animals and lead to immediate problems that hinder the success of your aquarium. So, like most aspects of aquarium keeping, patience is key.
Acclimation guide by Live Aquaria:
Aqueon tips for a healthy aquarium: