I wrote this up a little while back.
Acclimation Procedures For Fish, Corals, and Invertebrates
Proper acclimation of your fish, corals, and invertebrates is very important for the long-term survival of your animals. Acclimate is defined as “to accustom or become accustomed to a new environment or situationâ€. So, when we acclimate our fish, corals, and invertebrates we are making them accustomed to the new environment (our tank) that they will be put into.
Acclimation procedures differ for fish, corals, and inverts but the end goal is the same, to make the transition of these animals as stress free as possible. When acclimating we are trying to get these animals used to parameters in our tanks. The most important being temperature, salinity, and pH. Here are some of the more popular acclimation procedures.
Float Method
This method of acclimation can be used for both fish and corals but is not recommended for inverts, as they can tend to be a bit more sensitive.
1) Place bag with new fish/coral unopened into your tank and allow to float for between 10-15 minutes. By doing this you will slowly match the temperature of the water in the bag to that of your tank water.
2) Open the bag. Using a clean container (preferably a measuring cup) add about a half cup of aquarium water every 5 minutes or so until the bag is full.
3) Empty out about half of the water from the bag into another container. (Never add this water to your tank).
4) Again add about a half cup of water every 5 minutes or so until the bag is full.
5) Now your new arrival is ready to be added to your tank. Remove fish/coral from the bag (use a net for fish) and add to your tank. The water from the bag should be discarded. Never add this water to your tank.
As a side note with fish that have been shipped many people will turn off the tank lights for about 4 hours so the intense light will not stress the fish that has been in the dark for a while.
Drip Method
This method of acclimation will take slightly longer than the “float†method, but in my opinion is a gentler means of acclimation. First lets start with what is needed for this method. You will need a container that is small enough so that the fish/coral/invert is submerged by the water from its original bag yet large enough to handle more water. (I usually use a 5-gallon bucket and if the water does not cover the specimen, I use a towel to prop the bucket up on an angle) A length of airline is also needed and should be long enough to reach from the top of the tank to the bottom of the bucket. An airline valve is very helpful as well but this method can be done without it. A suction cup with a clip used for holding airline in a tank is also useful but again not totally necessary. A timer of some kind will also help (I usually use my cell phone).
1) Take the container that you have decided to use and put the specimen along with all the water that is in the bag it came in into the container. If need be prop up one side of the container to ensure the specimen is completely covered with water.
2) Now take the length of airline and put one end into your tank. This is where the suction cup used for airline is helpful; it will hold the end underwater.
3) Take other end of the airline and attach the airline valve if you have one. If you do not have one tie 2-3 loose knots in your airline.
4) Start a siphon in your airline by sucking one the end that is out of the water. Once the water starts to come out the end, it is time to adjust the flow. If you are using an airline valve simply, use the valve to slow the flow to about 2-4 drips per second. If you are not using a valve, the loose knots you put into the line will be used to adjust the flow. Pull the knots tight to slow the flow or loosen to speed up the flow. Just like with the valve 2-4 drips per second is the goal.
5) Position the airline so that it drips into the bucket where your specimen is. The goal is to double the amount of water in the container. Here is where I start a timer on my phone for 40 minutes. This is usually a sufficient amount of time.
6) After the 40 or so minutes the amount of water that you started with should have just about doubled. It is now time to move your specimen from the container to the tank. The use of a net is recommended for fish and for corals/most inverts I will use my hands. Make sure not to add any of the water from the container back into your tank.
7) After your specimen is safely in your tank, discard the water in the container making sure not to put any into your tank.
8) Something to consider with this method is the temperature of the water in the container because it can cool down rather quickly “outside†of the tank. If I am doing an extended drip, (for sensitive animals) I have a small heater that I use for the container. You must also remember that you are removing saltwater from your tank, so when topping it back off you must use saltwater not fresh to keep that salinity from really fluctuating.
It is also worth noting that some inverts and ever some fish may require additional time acclimating. This is because some of these animals can be extremely sensitive to changes in parameters.