How to Acclimate Fish: Matching Temperature and Water, Drip and Cup Method Steps and Timing, and Notes for Shrimp, Medaka and Goldfish

In short: how do you acclimate fish?

Float the bag to match the temperature, then add tank water little by little to get the animals used to the water. At the end, scoop out only the animals with a net and throw away the bag water.

Acclimation is the process of slowly moving animals from the shop's water to the water in your tank at home. Shop guides and manufacturers' guides both recommend it as the basic step when adding new animals.

The confusing part is time. Sources range from "30 minutes" to "1 hour" to "2 hours or more." It is easy to be unsure which one to follow.

What this article covers:

• The difference between temperature acclimation and water acclimation
• Steps for the cup method and the drip method
• How long it takes, and when to take longer
• Why bag water should not go into the tank
• Acclimating shrimp, medaka and goldfish
• What to do on the day you bring them home

First, a quick reference for this page. Choose how long to acclimate based on the animal and how different the water is.

The key point: the bigger the difference and the more delicate the animal, the longer acclimation should take.

What is acclimation, and how do temperature and water acclimation differ?

Acclimation has two parts: temperature acclimation and water acclimation. The first brings the water temperatures together, and the second gets the animals used to what is in the water.

It is hard to feel a temperature difference by hand. Floating the bag brings the water inside it close to the tank temperature.

What is in the water differs from shop to shop and from home to home. Acclimate in this order: match the temperature first, then get them used to what is in the water.

What happens if you do not acclimate fish?

Without acclimation, sudden changes in temperature or water can weaken the animals. A University of Florida guide says sudden temperature change puts heavy stress on fish.

The University of Florida (UF/IFAS) guide covers acclimation after fish are transported.

• In shipping water, carbon dioxide builds up and the pH tends to drop
• When temperature and pH rise, ammonia changes to a more harmful form
• Add tank water little by little to prevent sudden changes in temperature and pH
• When the temperature difference is large, take 2 hours or more

Tokyo Aqua Garden's guide also says skipping it can lead to weakness or disease. The effort of acclimation is insurance against weakening them right after they go in.

How long do you float the bag to acclimate the temperature?

Float the closed bag in the tank for about 30 minutes. GEX's guide says about 30 minutes, and Tokyo Aqua Garden says 30 minutes to 1 hour.

Steps for temperature acclimation:

1. Turn off the tank light
2. Float the closed bag on the water surface
3. Move it to the edge so it does not sink or tip over
4. Wait about 30 minutes so the water in the bag and the tank reach the same temperature

The US aquarium store Aquarium Co-Op says 10 to 15 minutes is enough if the bag stays closed. The goal is to match the temperature.

For breathable bags, it says to set them on top of the lid for 30 to 60 minutes instead of floating them. If you are not sure what kind of bag you have, ask the shop when you buy, and you will not have to guess.

How do you acclimate fish with the cup method?

In the cup method, you move the animals with their bag water into a container and add tank water a cup at a time. It needs few tools and suits hardy fish.

Here are Aquarium Co-Op's steps, with the tools swapped for things you probably have at home.

1. After temperature acclimation, move the animals with their bag water into a bucket or container
2. Add about as much tank water as there is water in the container
3. After 15 minutes, add about the same amount again
4. After 10 more minutes, add once more
5. Scoop out only the animals with a net and move them to the tank

If the container is about to overflow, pour some out along the way. Each addition doubles the volume, so after three additions most of the water in the container is tank water.

Tokyo Aqua Garden's guide also shows adding water with a large pipette instead of a cup. Keep the container somewhere it stays close to the tank temperature.

How do you do drip acclimation?

In drip acclimation, a thin tube drips tank water into the container one drop at a time. It changes the water slowly over time, so it suits shrimp and fish sensitive to changing water.

GEX's red bee shrimp guide lists these tools.

Steps for drip acclimation:

1. After temperature acclimation, move the animals with their bag water into the container
2. Put one end of the tube in the tank and fix it with the suction cup
3. Suck on the other end to start the flow, then hold it over the container
4. Narrow the flow to a slow drip with the valve, or by tying a knot in the tube
5. When the container fills up, pour out about a third and keep going
6. Once the water is well mixed, move only the animals to the tank

Tokyo Aqua Garden's guide says to repeat this pour-out-and-refill cycle 3 to 4 times. It gives about 40 to 60 minutes as the time the drip method takes.

With the drip method, the drip speed sets the time. If it is too fast, it is no different from the cup method.

How long does acclimation take in total?

For hardy fish, about 1 hour in total is a rough guide. With a large temperature difference or delicate animals, it can take 2 hours or more.

Here are the times from each source.

The numbers vary because the assumptions vary. Use three things to find your row in the table: the temperature gap between shop and home, how delicate the animal is, and the method.

If acclimation goes on too long, the water in the container can cool down. If you take a long time in winter, keep the container next to the tank and check the temperature now and then.

Why shouldn't bag water go into the tank?

Bag water contains waste from the animals' droppings and germs from the shop's tanks. At the end, scoop out only the animals with a net and move them.

Sources give slightly different reasons for keeping bag water out.

There is also a method, as in GEX's guide, where you open the bag, mix in tank water and wait for the fish to swim out on their own. In that case a little bag water goes into the tank.

For animals shipped a long way, or tanks you want to keep free of disease, keeping bag water out is the safer choice.

Why does shrimp acclimation take longer?

Because shrimp do not handle sudden changes in temperature or water well. GEX's guide says moving them all at once can weaken them or even kill them.

Reasons to take time acclimating shrimp:

• Some sources say they are sensitive to changes in their surroundings (red bee shrimp)
• They grow by shedding their shell (molting), so what is in the water, which they use to build a shell, matters
• Some sources say they are sensitive to chemicals (Amano shrimp)

Aquarium Co-Op says shrimp need minerals in the water to build a new shell. The University of Florida guide also describes how molting works.

Here are the temperature and pH preferences of the shrimp and snail covered on this site.

Source (4)

• GEX (temperature), Tokyo Aqua Garden (pH, level, temperament), Kyoto Prefecture Red Data Book 2015 (size)
• Aquarium Co-Op (temperature, pH), UF/IFAS EDIS IN1301 (size, habitat)
• GEX (temperature), Tokyo Aqua Garden (pH, level), Hyogo Prefecture Red Data Book (size)
• Tokyo Aqua Garden (temperature, pH, temperament), Ishikawa Prefecture Red Data Book (size)

Acclimate shrimp slowly with the drip method. With shrimp, keeping a steady drop-by-drop pace matters more than how many minutes it takes.

Compatibility with fish kept alongside shrimp is covered in Shrimp Tank Mates.

Is acclimating medaka or goldfish different from tropical fish?

For medaka and goldfish too, the order is the same: temperature first, then water. The difference is temperature: in a tank without a heater, the water temperature changes a lot with the seasons.

Medaka and goldfish are fish that do not need a heater. Next to tropical fish, they prefer different water temperatures.

Source (4)

• Seriously Fish (Paracheirodon innesi)
• Seriously Fish (Poecilia reticulata)
• Seriously Fish (Oryzias latipes)
• RSPCA Australia: How should I care for my goldfish?

GEX's guide on medaka tanks says to match the temperature especially carefully before adding them. In a tank with no heater, the water temperature follows the room temperature.

Check the tank thermometer before floating the bag. If it looks very different from the shop's water temperature, take your time with the drip method.

Choosing partners for medaka and goldfish is covered in Medaka Tank Mates and Goldfish Tank Mates.

Besides acclimation, what should you do on the day you bring fish home?

On the day you bring them home, decide whether to use a quarantine tank, dim the lights and feed lightly. After adding them, watch how they swim and breathe.

Based on the University of Florida guide and manufacturers' guides:

The University of Florida guide recommends watching new fish in a separate tank for at least 30 days. Acclimate them the same way when moving them into the quarantine tank.

What are common mistakes when acclimating fish?

There are three common mistakes when acclimating fish. They are cutting temperature acclimation short, pouring in the bag water, and dripping too fast.

When in doubt about acclimation, choosing the slower option leads to fewer mistakes. But the longer it takes, the more you need to watch the container's temperature and oxygen.

What terms come up with acclimation?

What else goes with acclimation?

Acclimation is tied to compatibility between the animals you add and the ones already in the tank. Check the partners in these articles before you add anything.

• Adding shrimp: Shrimp Tank Mates
• Adding medaka: Medaka Tank Mates
• Adding goldfish: Goldfish Tank Mates
• All 23 species together: Tropical Fish Tank Mates Chart

What are common questions about acclimating fish?

How many minutes does it take to acclimate fish?

For hardy fish, about 30 minutes for temperature and about 30 minutes for water is a rough guide. For shrimp and delicate fish, take longer with the drip method.

When the temperature difference is large, it can take 2 hours or more.

What happens if you do not acclimate fish?

Sudden changes in temperature or water can weaken them or make them sick. Shrimp in particular do not handle change well.

At the very least, do temperature acclimation for every animal.

Do medaka need to be acclimated?

Yes. GEX's guide also says to match the temperature especially carefully before adding them.

In a tank with no heater, the temperature changes with the seasons, so take extra care with temperature acclimation.

Which is better, the drip method or the cup method?

The drip method suits shrimp and fish sensitive to changing water. For hardy small fish, the cup method works too.

If you are unsure, choose the drip method, which lets you take your time.

Can I put the fish into the tank in the bag?

During temperature acclimation, float the bag with it closed. When you release them, scoop out only the animals with a net.

Throw the bag water away instead of adding it to the tank.

Can I feed them right after acclimation?

On the first day, give only a small amount they can finish. Leftover food dirties the water.

Once they settle down and start swimming around, bring the amount back up little by little.

Sources

• UF/IFAS EDIS FA119: On-Farm Transport of Ornamental Fish (carbon dioxide and pH in shipping water, ammonia becomes more harmful as temperature and pH rise, adding tank water little by little, harm from sudden temperature change, 2 hours or more for a large temperature difference)
• UF/IFAS EDIS FA006: Ichthyophthirius multifiliis (White Spot) Infections in Fish (watch new fish for at least 30 days)
• UF/IFAS EDIS FA124: The Ornamental Fish Trade (watching fish before adding them, releasing them after getting them used to the water)
• UF/IFAS EDIS IN1301: Cherry shrimp (grows by molting)
• GEX: What to watch for between buying fish at the shop and releasing them into your tank (お店でお魚を買ってから、家の水槽に放すまでの注意点, in Japanese. Float the bag about 30 minutes, open the bag and mix in water and wait for the fish to come out, drip method or similar for fish sensitive to changing water)
• GEX: Let's keep the popular red bee shrimp! (大人気！レッドビーシュリンプを飼おう！, in Japanese. 30 minutes of temperature acclimation, drip method tools and steps, moving them all at once can weaken or kill them)
• GEX: Peace of mind for your first six months (これで安心。スタートしてから半年までに, in Japanese. Acclimation, especially matching the temperature before adding them, moving fish with bag water into a bucket and adding tank water little by little)
• GEX: The best algae eaters for tropical fish, by type of algae (【コケ種類別】熱帯魚飼育におすすめのコケ取り名人, in Japanese. Too much food dirties the water)
• Tokyo Aqua Garden: How to acclimate tropical and ornamental fish (熱帯魚・観賞魚の水合わせ方法, in Japanese. Float 30 minutes to 1 hour, water acclimation 30 to 60 minutes, drip method 40 to 60 minutes, pour out a third and repeat 3 to 4 times, germs in bag water, drip method for shrimp, aeration for animals weak to low oxygen, skipping it can cause weakness or disease)
• Tokyo Aqua Garden: Amano shrimp (ヤマトヌマエビ, in Japanese. Sensitive to chemicals)
• Aquarium Co-Op: How to Acclimate New Aquarium Fish (closed bags 10 to 15 minutes, breathable bags on the lid for 30 to 60 minutes, cup method steps, ammonia and carbon dioxide in the bag, darkness helps fish calm down)
• Aquarium Co-Op: Cherry Shrimp Care (shrimp need minerals in the water to build a new shell)