How to Change the Fish Tank Water

How to Change the Fish Tank Water?

It’s vital to comprehend the ins and outs of changing your fish tank water to ensure your fish remain happy and healthy. With thousands of fish breeds out there, each requiring a different level of care, it’s important to remember that your fish’s overall health reflects their aquarium. Maintaining a spick-and-span tank not only enhances their well-being but also prolongs their lifespan.

Generally, it’s important to monitor your tank’s pH and water levels daily. If you have a saltwater tank, it’s also important to maintain appropriate salinity levels. In this guide, we’ll show you the ropes of changing your fish tank water, from checking the water quality to replenishing the tank with fresh, clean water. You can keep your fish in the pink of health and happiness with a little elbow grease and attention to detail.

Why Change the Water?

Changing the water in your fish tank serves two major purposes: it keeps the water quality top-notch and helps prevent fish diseases. So, let’s dive into why it’s important!

Water Quality Matters:

Fish produce ammonia waste, which can build up and become toxic if left unchecked. Regularly changing the water removes excess ammonia and other pollutants, creating a healthy and stable aquatic habitat for your fishy friends.

Say No to Fish Diseases:

Dirty water can lead to fish health issues like fin rot, bacterial infections, and parasitic infestations. Changing the water eliminates harmful bacteria, parasites, and other nasties that could harm your fish. This keeps them happy and reduces the risk of diseases.

How to change the fish tank water?

Preparing Your Supplies

Before changing the water in your fish tank, gather all the supplies you’ll need. It should include sponges, a gravel or sand siphon, and two clean buckets (for saltwater fish). If you have saltwater fish, you’ll also need a saltwater mixture. Make sure that you clean the inside of the glass before you start replacing the water.

Preparing Your Buckets

You’ll need one bucket for newly mixed saltwater (if you have saltwater fish) and another to empty the existing tank water. It’s important to ensure you only remove as much water as you can replace when changing the water in the aquarium. If you have saltwater fish, refer to the instructions on your aquarium salt for the correct salinity level. You can prepare and store the water beforehand. Avoid using fresh tap water because it has dangerous additives for pet fish.

Removing Debris

As you work to remove debris from the bottom of your fish tank, work methodically using a sand or gravel siphon. Take time and work slowly to avoid damaging the tank or injuring your fish. It will help ensure you don’t harm your fish in the process.

Repeat the Process

Keep the tank levels at most 25% per water change as you siphon out debris. Repeating the process ensures that most of the debris gets cleaned up. It will help ensure your fish can easily acclimate to the new water without shocking their system.

Refilling Your Tank

After you’ve removed debris and siphoned out the old water, it’s time to refill your tank. Test the water to ensure you reach the appropriate pH and saline levels. Gradually pour the water that was removed during cleaning back into the mixture. Once you’ve refilled the tank, plug your filter in to remove any remaining debris. With these steps, you can help ensure your fish stay healthy and happy in their clean tank.

Why do you need to change fish tank water?

It’s crucial to change the water in your fish tank regularly. Fish waste, leftover food, decaying organic matter, and other factors can all contribute to declining water quality over time. If left unchecked, this can lead to dangerous levels of toxins such as ammonia, nitrite, and nitrate, which can cause stress and illness in fish.

Regular water changes help to mitigate these issues by removing harmful compounds and replacing them with fresh, clean water. It not only promotes a healthier environment for your fish, but it also replenishes important trace elements and minerals that are essential for their well-being.

In addition to these benefits, changing fish tank water can also help to control the growth of algae and prevent the buildup of debris and sediment on the tank’s bottom. It can improve the overall appearance of the tank and create a more aesthetically pleasing environment for you and your fish.

Ultimately, changing fish tank water is an important aspect of aquarium maintenance that should be considered. By following a regular schedule and monitoring the specific needs of your aquarium, you can help ensure that your fish remain healthy, happy, and thriving.

Tips for changing fish tank water:

Here are some steps for safe and effective water changes for your fish tank.

  • Regularly changing fish tank water is important to remove food and waste particles, which can convert into harmful chemicals like nitrate and phosphate.
  • Changing water is also necessary to reintroduce elements and minerals for fish’s well-being, which are used or filtered out of the water over time.
  • Veterinarians advise against completely cleaning and replacing freshwater tank water as it may shock fish’s system.
  • Removing fish from the tank causes unnecessary stress and risk of injury, so keeping them in the tank during cleaning is better.
  • Partial water changes are the best option to keep the tank clean without removing beneficial bacteria and resetting the nitrogen cycle.
  • Changing 10%-15% of the water each week for a smaller tank and 20% for a larger tank is recommended.
  • Allow tap water to sit for three days, and use a de-chlorinator before pouring fresh water into the tank.
  • Test the water quality daily to ensure balanced pH levels and maintain the natural balance supporting fish health.


Q1: How often do you need to change fish tank water?

A: Fish tank water should be changed regularly to maintain a healthy and clean environment for the fish. Changing 10-15% of the water in a small tank and 20% in a larger tank each week is recommended. However, the frequency and amount of water change may vary depending on factors such as the number of fish, the size of the tank, and the filtration system.

Q2: Can I use tap water to change the fish tank?

A: Tap water in a freshwater aquarium is possible but requires some preventive measures. It is because most municipalities use chlorine or chloramine to treat drinking water for disinfection purposes.


Changing the water in your fish tank is crucial for maintaining a healthy and balanced environment for your fish. It is important to understand the risks of completely replacing the water, as it can harm the beneficial bacteria in the tank and disrupt the nitrogen cycle, which could be deadly for your fish. Instead, partial water changes should be done regularly to reintroduce necessary elements and minerals while maintaining the natural balance of the tank. Remember to use a de-chlorinator and test water quality regularly to ensure a healthy and thriving fish tank.

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