Acclimating Fish      
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Thursday, 07 June 2007

Side Story

Proper acclimation of fish and invertebrates is something that we all need to do, however not all of us acclimate or at least not properly.  Acclimating is defined at as “to adapt to a new temperature, altitude, climate, environment, or situation intransitive verb.”

What does this mean you ask? Imagine yourself at the base of Mount Everest. Now imagine that there are 2 ways to get to the summit of Everest. (The summit is 29,000 feet above sea level) The first option is to run to the top as fast as you can. The second is to take your time and let your body adjust.  The first idea isn’t a good one and here’s why.  The oxygen level below 8,000 feet above sea level is similar enough that a body can adjust pretty easily. Below this level a change in altitude can lead to dizziness, light headedness or upset stomach.  Above 8,000 the oxygen content is so low that it could cause Altitude Sickness leading to possible death. The way around altitude sickness is taking your time and letting your body adjust. Well, that will reduce the risk anyways. Fish feel changes like that as well except ANY sudden change can possibly lead to death.


In this article I will show you a few ways to acclimate your fish and corals. Some people acclimate their fish and corals in exactly the same way but I prefer to acclimate my corals a little longer than my fish. Most veterans have their own proven way of acclimating fish and inverts but they had to start somewhere. 


Here are a few reasons why fish need to be acclimated:


1.   Temperature – Temperature should be the first thing to monitor when transporting a new inhabitant as well as the first step in acclimating your new fish or coral.  I purchased a digital thermometer in order keep a close accurate eye on the temperature.  Everyone knows the temperature of their tank bu,t do you really know the temperature of the water in the bag?  Usually when I arrive home with my new addition the water is anywhere from 72-78 degrees.  I keep my tank at 80-82 degrees. That’s a big difference so make sure you check the temperature first thing.

2.   Salinity – Salinity, expressed in parts per thousand (ppt) or specific gravity (SpG) expressed as a number like 1.025, is a measure of the salt mix in your water. It is one of the most important reasons to acclimate your fish. Many local fish stores (LFS) keep their SpG at a lower level than we like to keep our reef tanks. A lower SpG is less stressful to fish (this only applies to fish and not corals or inverts) and can lower the incidence of parasites. Not all fish stores use this method so you should check the SpG of the water in the bag. It seems as if almost every hobbyist has or wants a clown so I will use them as an example. Clowns (generally speaking) maintain a salinity of about 11 ppt within their body, By contrast  natural sea water is about 35 ppt. As we loose water in the form of sweat, fish do the same. As they loose this water they have to take in more or they will dehydrate just like humans. Fish control the balance of water using a process called Osmoregulation. They literally drink the water and using their kidneys and gills the excess salt is then excreted to maintain the right level of salt in the blood stream. In short the lower the SpG of a tank is the less work the fish’s body has to do to survive. You can equate this to a human’s body and temperature. The hotter it is outside (or colder) the more the body has to work to keep the core temperature of your body right.


There are other elements and compounds such as calcium, phosphates, ammonia, nitrates, and nitrites that need to be equalized. Depending on how you supplement your tank, iodine, magnesium and other trace elements might need to be equalized as well.


These are the 2 common methods to acclimate your fish and corals.


1.   Drip Method: This is the preferred method of acclimation. It uses a food safe container or small aquarium and a steady drip of water from your tank. This method is used by most successful reeferkeepers and is highly recommended for delicate fish and all corals.

2.   Bag Method: A less preferred method of acclimation using the bag from the LFS. This is used for hardier fish such as damsels.


The drip method is the safest, slowest way to acclimate your new critter. The bag method is equal to walking up Everest at a medium pace instead of running. It can be used for hardier fish but is not a preferred method. I highly and strongly recommend the drip method.


The drip method takes a bit of preparation. The concept of this method is to siphon water from your tank into the container with your fish. Here is a list of the supplies you will need.


1.   Air line tubing

2.   Air line valve

3.   2 small clamps – I use strong potato chip bag clamps.

4.   Food safe container or small aquarium.



Begin by placing the new fish or coral into your small aquarium of food safe container. This is sometimes a hard task. Depending upon how much water the LFS adds to the bag with your new inhabitant you might have to use more than one container. Some containers are wider than others and you might not have enough water from the store to cover the fish or coral in a larger container. A container with a smaller diameter will bring the water level higher. I have several containers that I like to use. Remember to be careful placing the inhabitant into the container.  You should never dump the water and fish into the container. This can lead to the fish slamming against the side of the container possibly causing injury and stress. Use a net to gently remove your new fish from the bag, pour the water into the container and then add your fish to the container.


Once the fish or coral is in the container simply place the container in front of or under your tank. Mark the outside of the container so you know how much water you started with. You can use a piece of tape or a marker.  Next, setup the tubing for the drip according to the following directions.

  1. Cut the tubing so that it will reach from a few inches below the water line of your aquarium and into the top of the acclimation container. Depending on where the container sits relative to your tank you might need 3 to 6 feet.
  2. Cut this tubing roughly in half and insert the air valve.
  3. With your clamps clamp the top tubing into the display tank. I like to leave 4-6 inches submersed in the established water.
  4. Place the other end of the line into your food safe container. This time you will want to leave the tubing above the water line so you can see how fast the water is dripping into the container.
  5. At this point you can stick your thermometer probe into the container so you can keep an eye on the temp.
  6. Now you are ready to start the siphon. I usually just suck on the end that is attached to the container. Another option is to fill the tubing with water before securing it to your aquarium and the acclimation container. Keep your thumb over the end of the tubing until you have the top and bottom secured. Remove your finger and your siphon will start.
  7. Once the water is running you will want to adjust the valve to a steady drip. One drip every 1-2 seconds is where I like to keep it at.
  8. Keep an eye on the container and the inhabitant for any sudden changes in the inhabitant’s movement and breathing.
  9. Let the water line rise at least twice as high of the mark and then turn the valve off.
  10. At this point I usually let the critter sit in the acclimation container for a few more minutes. The over all time-frame for this method can range from 45 minutes to a few hours. The more fragile the fish is the longer and slower you want its acclimation period to be.
  11. Once the inhabitant is acclimated and before introducing it into your aquarium I recommend feeding the tank, this will reduce the risk of any attacks from other fish. This is obviously not applicable if there are no other fish in the tank.
  12. Turn the lights off to help reduce the stress of the new fish.
  13. Now its time to introduce your new inhabitant to its new home. For fish, use a net to gently catch the fish and place in your tank. For corals use gloves to reach in and carefully pick up the coral. Try to avoid touching any living part of the coral and place into your tank.
  14. Wait an hour or two and resume your lighting schedule.


Never introduce the water in the acclimation container into your setup. This can lead to problems. You don’t want to take a chance that you might introduce a parasite or disease into your aquarium. Furthermore many stores routinely treat the water in their fish aquariums with copper and this is deadly to invertebrates.


Also keep in mind that everything (rocks, fish, cleanup crew, and corals) you introduce to your aquarium needs to be quarantined! This will help make sure that you don’t introduce a parasite or pathogen to your aquarium.  Skipping quarantine leads to big headaches sooner or later. While in quarantine you might see anything from aiptasia to unwanted crabs, ich to velvet. I like to leave newly acquired livestock in the QT tank for at least 4-6 weeks.


When you move inhabitants from your quarantine tank to your display tank you will want to acclimate them as well. Every time you change the environment you need to acclimate the livestock to the new condition. This can be a pain sometimes but it sure beats getting an outbreak of aiptasia or flat worms. Extra work now will save you from Emergency work later. Check out this article on Quarantining.


The less preferred practice is the bag method. Unfortunately, this method is often recommended to new hobbyists. All too often their new purchase dies, usually due to the shock of this procedure. If a creature is hardy this method may work but I highly recommend using the Drip Method any time you acclimate. Nonetheless I am going to explain it so you know the concept.


The bag method is easy and requires less preparation than the drip method. However, as I said before, this method shouldn’t be used except with very hardy fish. Never acclimate corals using the bag method.  Simply place the bag in the top of your tank and let it float for a while to adjust the temperature. Then, open the bag and being careful to not introduce any of the water from the bag into your aquarium add tank water equal to 1/4th of the amount of water that’s in the bag. For example, if the bag has 4 cups of water in it you will want to add 1 cup of tank water. Add this water very slowly then re-seal the bag and let it float for another 30 minutes. Repeat this process until you have increased the water volume in the bag one and a half times. In our example this means adding 6 cups of tank water to the bag giving you a total of 10 cups of water. Depending upon the size of the bag you may have to remove and discard some of the water before you are done. Once again do not add any of the water from the bag back into your tank! Once the steps are completed take a net or a glove and place the inhabitant into your tank.



Depending on the species it can be a few days before you really start to see the fish comfortable and acting normally in your tank.  There have been reports of certain gobies and tangs hiding for weeks while they become comfortable in their new home. They are just getting used to their new environment and tank mates.


Remember, our pets can not take care of themselves and we need to take extra steps to keep them comfortable and healthy in their environment. Rather than survive we need to make sure they thrive.






Last Updated ( Wednesday, 13 June 2007 )
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