How Long to Light off When Adding New Fish

How Long to Light off When Adding New Fish

Adding new Fish to your aquarium can be an exciting and rewarding experience. However, it’s important to consider the impact that the lighting in your tank can have on your new aquatic friends. 

Aquarium lighting plays a crucial role in the health and well-being of your Fish and plants. It can affect everything from their growth to their behaviour and overall appearance.

As a result, it’s essential to understand how lighting relates to your Fish and how to manage it when introducing new Fish to your tank properly. 

One of the most common questions asked by aquarium owners is how long to keep lights off when adding new Fish.

In this blog post, we’ll explore this topic in-depth and provide helpful tips on managing aquarium lighting when adding new Fish to your tank.

How Long to Keep Lights off When Adding New Fish

When adding new Fish to an aquarium, it’s generally recommended to keep the lights off for several hours to reduce stress on the Fish.

The duration of time you should keep the lights off depends on a few factors, such as the species of Fish, their level of sensitivity to light, and the overall condition of the aquarium.

Generally, it’s a good idea to keep the lights off for at least 2-3 hours after adding new Fish to the aquarium.

This will give them time to acclimate to their new surroundings and reduce stress caused by sudden changes in lighting.

Some species of Fish are more sensitive to light than others and may require a longer period of darkness to adjust.

It’s also important to note that turning off the lights will help reduce the Fish’s stress levels during transportation and the acclimation process.

When Fish are stressed, they are more susceptible to disease and other health problems, so taking steps to minimize stress is important for their overall well-being.

After the initial period of darkness, you can gradually increase the lighting levels over several days, monitoring the Fish closely for signs of stress or illness.

With proper care and attention, your new Fish should adjust well to their new home and thrive in their aquarium.

New Arrival Acclimation Guide

When introducing new aquatic life to your aquarium, it is important to acclimate them properly to ensure their successful relocation.

The water that the Fish or corals are stored in has different temperature, pH, and salinity parameters than your aquarium.

Fish, especially invertebrates (such as corals), can be affected by even small changes in these parameters, so proper acclimation is crucial.

There are two recommended acclimation methods that you can use:

Drip acclimation method

The drip acclimation method is a process used by aquarists to acclimate new Fish to the water conditions of their aquariums slowly.

The method adjusts the temperature, pH, hardness, and other water parameters of the water in the Fish’s bag to match the aquarium’s water conditions.

The drip method is preferred because it is gentle, easy to do, and takes only 30 minutes to an hour, depending on the drip rate.

Here are the steps to follow to acclimate your new Fish using the drip method:

Step 1 

Collect Fish: When you purchase your Fish, the seller will put them in a plastic bag with water from the stock tank.

Ensure the bag is in a dark and silent place during transportation. Avoid shaking the bag too much or placing it where it may get too hot or cold.

Step 2

Put the Fish into a Bucket: When you get home, carefully transfer the Fish and the water from the bag into a plastic bucket. If the water is not enough to cover the Fish, tilt the bucket to increase the depth.

Step 3

Set up the Siphon:

  1. Tie several loose knots in an airline tubing to control the flow of water.
  2. Place one end of the tubing in the aquarium and the other end in the bucket.
  3. Suck on the end of the tubing to start the siphon.
  4. Once the water starts to flow, tighten the knots until the flow is about 4-5 drips per second.

Step 4

Half the Water: Wait until the water volume in the bucket has doubled, then stop the siphon and remove half of the water from the bucket. Start the siphon again and repeat the process until the water volume in the bucket has doubled twice.

Step 5

Turn off Lights & Introduce Fish to New Tank:

  1. Leave the lights off for 3-4 hours after the new Fish are introduced in the tank. It helps to prevent sudden changes in the tank temperature during acclimation.
  2. Put the Fish in the bucket using a net, ensure the net is much larger than the Fish.
  3. Place the net in the tank water and let the Fish swim out.
  4. Do not put any water from the bucket into your tank.

You can also put your fish in a bucket or pitcher then Incorporate a cup of water from your tank every 4-5 minutes instead of using the drip method.

Whenever the bucket’s volume of water doubles, repeat the step, discard half the volume, and keep repeating until the volume of water doubles again.

This method is not as good as the drip method, but it is better than the floating method.

Float and add method 

The floating method is a popular technique for acclimating Fish to a new aquarium. It involves slowly introducing the Fish to the new water conditions over a period of time to avoid any shock or stress caused by sudden changes in temperature, pH, or other water parameters. 

Here are the steps to follow when using the floating method:

  1. Switch off the aquarium light and dim the lights in the tank’s room. This will reduce the stress on the Fish and make it easier for them to adjust to the new environment.
  2. Float the bag containing the Fish in the aquarium water for 15-30 minutes. This will allow the temperature in the bag to adjust gradually to the temperature in the tank.
  3. Open the bag and roll the top edges down in order to create an air pocket. This will allow the bag to float as you add water from the tank to the bag.
  4. Add half a cup of water from the tank to the bag every 4 minutes until the bag is full.
  5. Take out half of the water from the bag and float the bag again. Repeat step 4, adding water from the tank to the bag every 4 minutes so that the bag is full again.
  6. Use a net to move the Fish from the bag to the tank. Be gentle and quick to minimize stress on the Fish.

It’s important to note that the floating method may not be appropriate for all types of Fish or all types of aquarium setups.

It’s always a good idea to research the specific needs of your Fish and consult with a knowledgeable aquarium professional if you have any questions or concerns.

Light acclimation

Light acclimation is gradually introducing a new fish to a new lighting environment. When a fish is moved from a pet store or one aquarium to another, it is important to acclimate it to the new lighting conditions gradually.

This is because abrupt changes in lighting can be stressful for the Fish and can even cause health problems.

To acclimate a new fish to a new lighting environment, follow these steps:

Dim the Lights 

Start by dimming the lights in the aquarium where the Fish will be placed. This can be achieved by turning off some of the lights or by using a dimmer switch.

This will help the Fish adjust to the new environment gradually.

Monitor the Fish

Watch the new Fish closely for signs of stress, such as rapid breathing or hiding. If you notice any signs of stress, reduce the lighting further.

Increase the Lights 

After a few days, gradually increase the lighting in the aquarium by turning on more lights or increasing the brightness of the lights.

Monitor the Fish closely for signs of stress and adjust the lighting as needed.

Maintain a Consistent Schedule 

Once the Fish has acclimated to the new lighting environment, it is important to maintain a consistent schedule.

This means keeping the lights on for the same amount of time each day and not making sudden changes to the lighting.

Use a Timer 

Using a timer to control the lighting can be helpful in maintaining a consistent schedule. Set the timer to turn the lights on and off at the same time each day.

Overall, light acclimation is a gradual process that requires patience and careful observation.

By taking the time to acclimate new Fish to their new lighting environment, you can help them adjust more easily and minimize stress.

Should the lights be off all day when adding a new fish?

No, it is not necessary to turn off the lights all day when adding a new fish to an aquarium. However, turning off the lights for a few hours after adding a new fish is recommended to help the Fish adjust to its new environment.

When a new fish is introduced to an aquarium, it may experience stress due to changes in water chemistry, temperature, and the presence of other Fish in the tank.

Turning off the lights for a few hours can help to reduce stress by creating a more subdued environment and giving the new fish time to acclimate to the tank.

It’s important to note that turning off the lights for too long can have negative consequences for the other inhabitants of the tank, such as plants and algae that need light to thrive.

So, turning off the lights for a few hours after adding a new fish is recommended, but leaving them off all day is not necessary.

How much light does a tank require?

Aquarium lighting is essential to creating a healthy and thriving aquarium environment. The amount of lights you need depends on the aquarium you have and the type of aquatic life you are keeping.

Planted Tank

A light with a colour temperature between 6500 to 7500 Kelvin is recommended for a planted tank. This type of light will promote plant growth and photosynthesis.

The recommended PAR (Photosynthetically Active Radiation) for low light plants is between 15-30, medium light plants between 30-80, and high light plants require 80+ PAR.

Fish Only Tank

Fish-only tanks require less intense lighting than planted tanks, typically between 5500 to 6500 Kelvin, which is similar to natural sunlight at noon.

Fish do not have a biological need for light, so the light is mainly for general viewing purposes.

Marine Tank

Marine reef tanks require a higher intensity of light, typically between 300-500+ PAR, to support the growth and health of soft and hard corals.


GloFish® is a new entry to aquatics, and these Fish fluoresce under blue spectrum light or black light, so using a blue light source is ideal for showcasing their vibrant colours.

However, choosing the proper lighting for your aquarium is crucial to maintaining your aquatic life’s health and well-being.


Proper light acclimation is essential for the health of your Fish when adding them to a new aquarium. Turning off the lights for 2-3 hours can help reduce stress and allow the Fish to acclimate to their new environment.

However, it’s important not to keep the lights off for too long, as Fish require light for their biological processes and overall health.

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