General Marine Acclimation Principles

Just as it is important to match fish with similar dispositions it is also important to acclimate fish properly. Acclimation is the process of gradually introducing a fish to its new surroundings and tank mates. It is much more than simply dripping the tank’s water into the bag over fifteen minutes. A new fish has to overcome three things when introduced into a new tank:

  1. The fish is usually stressed from capture and shipping before being placed in its permanent new home.
  2. It has to acclimate to its new home and
  3. Lastly it needs to fend off the aggression of the previous residents to the

For these reasons the initial two weeks after a fish is purchased is usually the time frame when they are at greatest risk. A newly purchased fish should not be simply dumped into the display tank, but it should be gradually acclimated to its new home in a separate tank to reduce the risk of it introducing a disease. This quarantine period also allows it to become accustomed to feeding in a captive system and also become accustomed to new water conditions. For these reasons one of three general philosophies of acclimating a new fish should be employed:

  1. In the best case a quarantine tank should be utilized to acclimate the fish as well as get it accustomed to eating. There are many articles dealing with quarantine tanks so we won't deal with them here. Also, since less than 2% of all fish keepers have quarantine tanks they are not how most people will be able to deal with this problem. In the case of a tank with a sump, the sump can be used as the initial home for the newly acquired fish. If a sump is available, it should be secured so that the pump intake is screened to make sure that the fish is not drawn into the pump intake and killed. The fish should be acclimated to the new water per the directions below. The fish should be kept in the sump for approximately two weeks at which time the next phase of acclimation should be...
  2. This next phase is what those of you who do not have a sump in place should do. In this phase a holding container is placed in the tank and the fish is placed in it. For this purpose a large (two gallons in size) clear plastic box is attached to the inside of the tank. Lots of holes are drilled in the bottom and sides of the box so that the tank's water can flow freely into the box. In addition the output from a powerhead can be directed to flow into the box so that there is constant new water flowing through the If a sump is unavailable the fish should follow the initial acclimation process outlined below and then placed in this box. This clear box allows the new fish to view its new surroundings and tank mates and in addition it allows the tank's residents to view their new tank mate. The clear box will also encourage any fish with aggressive tendencies to show them by charging the fish in the box. At first the fish in the box will cower when approached by the tank's residents. A lot of aggressive displaying will occur as well as mock aggression. However the clear box will prevent any damage from being done and over time (usually two to four days) the frequency and intensity of these attacks will diminish. By seeing which fish continue to attack you can also note where future attacks may come from. The fish should be kept in the box until no attacks occur, this may take from anywhere from 2 to 10 days. However even after this period of time attacks may continue. If after this time attacks are still occurring, even if infrequently, a next step needs to be taken.
  3. This step entails removing the aggressive individual or individuals and placing them in the box, while at the same time releasing the new individual into the tank. This step is necessary because the tank's older residents have established territories and know the tank's hiding places and if a new fish is introduced while they are still present the new fish will be at a distinct disadvantage which usually results in the new fish either getting killed outright or being harassed to such an extent that it never eats and eventually.

There are several things that can be done to reduce this aggression once the tank's older residents are re-released back into the tank. The coral or other landscaping materials can be rearranged in order to make the old fish establish a new territory. In addition, if the fish attempts to attack the newcomer even 

when it has been placed in the box then several new fish should be added to the tank before this older fish is released back into the tank. By adding more than one fish the aggressive tendencies of the older fish will be more spread out and thus each fish should be able to tolerate it. More than one fish needs to be introduced whenever you are adding a fish to a tank that already has a member of that same species, as fish are generally most aggressive when confronted with new members of their own species particularly damselfish, tangs and dwarf angelfish. In addition, they are also aggressive to members of their own genus as well as fish that are physically similar in terms of coloration or physical shape or fish, which have a similar diet. 

As mentioned above once you have set up a tank properly most fish are hardy and will do fine. Proper acclimation is as crucial as proper selection, as doing both properly will help to avoid problems with aggression, disease and nutrition. 

Having discussed general philosophies, we now move on to the actual acclimation procedures. The following procedures are recommended to safely and successfully introduce your newly arrived aquatic animals to your holding systems. More animals are lost due to poor or insufficient acclimation procedures than virtually any other factor. Moreover, it is not uncommon for animals to die days or even weeks after arrival specifically because they were stressed and/or damaged during acclimation. 

During shipping your new fish or invertebrate is confined inside a plastic bag without any of the normal filtration and temperature control it has been used to. Even though we ship using the latest and most advanced stress coats, ammonia reducers, and pH buffers, because the animals are alive all of their metabolic processes continue inside the bag without any way for their natural waste and respiratory products to be completely removed. Additionally, even packed in insulated containers with temperature packs, during shipping the animals can be exposed to greater temperature fluctuations than normal. The net result of all of this is a decrease in pH, a rise in ammonia, and often enough a temperature shock. All of these have a cumulative effect to put your animal into some degree of stress and even shock after transit.

On top of all of this, we hold all fish in hyposaline conditions (specific gravity of 1.018) to inhibit the proliferation and transmission of a variety of ubiquitous parasites and pathogens. If your system water is not hyposaline, the transition from hypo to relatively hyper saline water can be extremely stressful, if not fatal, when handled improperly.

“Acclimation” is simply a way to introduce the animals safely from the relatively toxic conditions of their shipping bags to the healthy and safe conditions of their new home. Even though you may think that it is important to get your animals out of the bag and into your clean holding systems as soon as possible, it is extremely important to remember that too rapid a change in water conditions can be far more dangerous to aquatic animals than being kept longer in a relatively bad environment. It is this slow transition from one aquatic environment to another that is the focus of our acclimation procedures.

REMEMBER – SLOW IS GOOD, so take your time!

We take great pride in holding our animals under exceptional care and husbandry regimes.

Having said that, please note that we recommend that all newly introduced animals be quarantined first to prevent the introduction of any potential disease and/or parasites to your aquarium systems. If you do not have a quarantine system available (and even if you do) it is important that a commercial “fish dip” be used prior to introducing new fish species into your holding systems. DO NOT use any “fish dip” on corals, clams, or invertebrates.