How Long Should I Acclimate My Fish? A Guide For Beginners

Purchasing new fish is arguably among the favorite activities of aquarists. Since nothing beats the joy of introducing new species to an aquarium, many people go out of their way to put as many fish inside a tank as possible.

That said, not everyone is familiar with the right introducing techniques. Too often, people will wonder “How long should I acclimate my fish?” and “How can I acclimate my fish properly?” If you are having the same problem, keep reading to find out the answer!

How Long Should I Acclimate My Fish?

acclimating fish

Many believe that a 15-minute acclimation is enough for a fish to transition from their bag to the tank.

While this is not entirely untrue, you are still advised to give your fish a little more time. In most cases, at least an hour staying inside a floating bag is recommended for newly bought fish to adjust themselves.

How To Acclimate A Fish Properly

If you are yet to know how to introduce a fish the right way, make sure to follow the step-by-step guidelines below.

Step 1: Bring your newly bought fish home immediately after leaving the pet store. This is because the carrying bag does not have enough oxygen for your fish, which may cause breathing difficulties. Furthermore, fish do not like being kept in narrow, crowded plastic bags.

Step 2: Turn off the tank lighting system and dim the lights of where you place the tank. If you put it somewhere with lots of natural light, draw the curtains. This helps them relax and not get worked up about being thrown in a brightly lit space.

Step 3: Wash the outside of the carrying plastic bag carefully. Use soap to sterilize any remaining germs and bacteria. If you throw the bag inside the tank without rinsing it off first, chances are your tank water will be contaminated.

Step 4: Slowly put the bag into the water tank. Open it up and roll it down roughly three times. This way, the bag can float safely inside the tank without compromising the oxygen supply.

Step 5: Let the bag stay on top of the tank for roughly 15 minutes. Wait until the temperature inside the bag is the same as the temperature inside the tank.

Step 6: Put half a cup of tank water into the floating bag. Repeat this procedure three to four times until the bag is full. This helps the fish become more familiar with the water composition, parameters, and other vital characteristics.

Step 7: Pull the bag out and empty half of its water. Put it back into the tank and repeat step 6 one more time. After you are done here, your fish can be safely released inside the aquarium.

Step 8: Do not pour the water directly inside the aquarium, as it may cause physical injuries and spoil your tank water. Instead, use a net and swoop the fish out. Then, gently place it inside the tank and let your fish enjoy its new home.


1. What happens if you don’t acclimate to fish?

Failing to acclimate fish before letting them inside a water tank can have detrimental effects.

Firstly, it may die from experiencing a pH shock. Differences in water compositions – including hardness, pH levels, ammonia, and nitrate levels – can render the fish inactive and cause severe health issues.

Secondly, your fish stands a higher chance of not being able to socialize with the pre-existing community at your home tank. If thrown directly inside the water, your newly bought fish may appear as a threat to others.

This is when a floating bag comes in handy. Letting the fish stay in the floating bag for a few hours first gives the other fish a chance to get to know the newcomer. Thus, conflicts are less likely to happen.

Thirdly, acclimating fish inside a bag prevents a sensory overload. Fish are highly sensitive to both sounds and lights. If poured directly inside a tank, they sure will be shocked. If the conditions are unfavorable, some might even end up dying!

2. How long can a fish stay in the bag to acclimate?

Some hardy fish can stay up to 24 hours inside a bag, but most are only comfortable with 9 hours only.

When it comes to fish acclimation, you may want to keep them there for roughly two hours at most. This is already plenty of time for fish to adjust themselves and minimize the impact of being stuffed in a plastic bag.

3. Should you feed fish after acclimation?

Not really. Research has shown how fish refuse to eat for at least a day after being introduced to a new tank. While some simply turn down food, others are more dramatic in their attempts to swim away and hide.

However, there are some fish wishing to be fed right after they join a new community. You can test this out simply by offering them a small pellet of food. If they take it, then feel free to start feeding them.

4. Do acclimation boxes work?

Acclimation boxes are like plastic bags, but they are attached to the tank. Like floating plastic bags, the goal is to give fish some time to adjust themselves. This way, they can freely enjoy the new environment after being fully introduced to the new water bodies.

Acclimation boxes are a simple yet effective idea, and they tend to work perfectly if the aquarists are attentive enough.


How long should I acclimate my fish? The answer ranges from 15 to 60 minutes, depending on which species you want to nurture. Remember to follow the acclimating guidelines carefully so that your newly introduced fish can stay healthy and happy.