by Peter McKane
of England. From his website www.helpthefish.org
The acclimatization of fish is an incredibly important process. Without it, fish that
you introduce to your tank, whether it is a new setup or not, will become severely
stressed and as a result may die or suffer severely reduced life expectancy. The process
itself is incredibly simple, and if more people stuck to it, then many stress related
deaths could be avoided.
Acclimatization begins where you first pick up the fish. From the moment they leave their
tank, whether it is from a private supplier, a local fish store or even out of the box
that they were delivered in, the fish must be kept as still as possible. If you are
driving home with your fish, then hold the fish in its box or bag in the air between your
legs. This means that any sudden acceleration or stopping will mean that the fish will
sway and not be bumped up against the side of their container. The container should also
let in as little light as possible. Most fish stores will wrap a bag containing fish in
old newspaper, and this is an excellent practice because dark conditions make fish suffer
less from stress.
If your journey back to the new tank for the fish is long, make sure that you open the
container at least once every thirty minutes to let in fresh air. This is not sufficient
to keep a fish happily alive for more than a few hours, because the container used to
transport the fish will be far below the recommended size to house the fish permanently.
This reason alone is enough to discourage buying fish that are delivered by post, unless
they are sent via a courier to arrive preferably within 12 hours, but no more than 24
Dark conditions make it much less likely to stress fish to the point of weakening their
immune system and making them susceptible to illness. Make sure that throughout the
process of moving the fish into its new aquarium, the fish sees as little light as
possible. Draw the curtains in the room and turn off any aquarium lights. Obviously you
will need to be able to see what you are doing, but as long as at least the aquarium
lights are turned off, then your fish will feel a lot happier about everything that is
Fish generally are very intolerant of rapid changes in their water conditions. A sudden
change in pH or KH can result in stress and illness. However, by far the most important
factor to consider is the change in temperature. A five degree sudden change in
temperature can be enough to cause most fish so much stress that they are likely to die
within a day of the change. For this reason, we will always float fish.
If you have ever seen your local fish store on the day of a delivery, you will
hopefully see that there are many bags with fish floating in the tanks that they will be
kept in until sold. Fish stores have a lot to lose if a whole batch of fish suddenly dies
from stress, and so they will usually take care to acclimatize their fish correctly.
Floating fish in bags or containers such as plastic boxes or breeding isolators means that
they will gradually become accustomed to the temperature of the tank. A fish should be
floated in darkness for at least fifteen minutes. I personally float my fish for anything
up to thirty minutes. While it seems to make sense to float a fish for as long as
possible, to reduce the stress of transportation and temperature difference, don't forget
that the fish is currently in a rather cramped environment, and a balance of introduction
speed to temperature acclimatization needs to be found. For me, thirty minutes is perfect.
It is also important to remember that even if the water in the transport container feels
like it is the same temperature as your own tank, your fish will like a rest from the
transport itself, and temperature is not the only thing to consider.
Now that your new addition is used to the temperature of your aquarium, you will need to
gradually add small amounts of water from your tank to the transport container. If the
transport container currently has a fish in four cups of water, then you should add one
cup of water from your own tank to this container every five to ten minutes. You should
aim to add, gradually, the same volume of water that is in your transport container from
your own tank over a period of fifteen to twenty minutes. Once you have done this, then it
is on to the method of introduction.
Many fish stores use the same water and a large filtration system over many tanks. This is
more efficient for the store and easier to maintain than having many individually filtered
tanks, and as long as there is no disease in the water, fish kept in a system like this
tend to thrive. However, always be aware that a single sick fish in one tank in a fish
store could indicate that the disease is present in all tanks. The last thing you want to
do is introduce a stressed and disease carrying fish into your own setup. The disease
itself may already be present in your own tank, like ich, but will be dormant because your
fish are healthy and resistant. Keep in mind that your new additions, no matter how well
transported, will be stressed, and therefore vulnerable.
It is always recommended that if you are introducing a new fish to your tank that you
do not introduce any new water to your own setup. Even if the fish you introduce is
perfectly healthy, the water may not be. Therefore, once you have gone through the
temperature and water condition acclimatization, you should catch your fish in a net and
then add them to your tank. You should also leave the lights off for at least an hour
after doing this.
This particular step must, however, be ignored for some types of fish. Puffers, for
example, must never be taken out of water because if they inhale air it is usually fatal.
In the case of fish that must be kept under water at all times, it is recommended that you
introduce as little of the new source water into your tank as possible. You should aim to
add twice the volume of water in the transport container from your own tank, and then use
a cup just big enough to hold the fish safely to take it from its transport container and
add it to your setup.
If you are a keeper of marine fish, then your fish are not only valuable as lives under
your responsibility, but also in terms of your wallet. Those aquarists who keep expensive
fish swear by enforcing a strict quarantine of all new fish. This is done by introducing
the newly acquired fish in a separate tank setup designed to be as close to the final
conditions that the fish will eventually be introduced to, but without the risk of
contaminating existing stock with diseases. Even if your fish are not expensive in terms
of how much they cost, you may want to consider doing this for all fish that you wish to
introduce into your tank setups. It is, by far, the safest way of ensuring that you do not
inadvertently introduce disease into your precious tanks. However, many aquarists,
especially beginners will not have the equipment necessary for this, and as such will
simply have to take the risk of introducing fish directly into their target tank.
This whole process, not including transportation, usually takes between thirty minutes
to an hour. Considering the benefits of healthy and stress-free fish, it is something that
can hardly be seen as a chore. Please follow these guidelines each time you introduce fish
to your tank, but do remember that no matter what precautions you take, fish do stress
easily, and if it is a weak fish then there is little that you can do to keep it alive.
Make sure to pick the strongest and healthiest fish from the stock that is available to
you, and if there are only sick or weak fish to choose from, then wait for a new delivery.
This sounds harsh, as the fish you leave behind may very well die and not be sold, but
this will only encourage breeders and fish stores to house their fish properly and keep
their fish as healthy as possible.