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Step-by-Step Guide: How to Change the Water in Your Fish Tank

Aqua One Horizon 65 Starter Kit includes Stand


Maintaining a clean and healthy environment for your fish is essential for their well-being.

One of the most important tasks in fish tank maintenance is changing the water.

Changing the water in your fish tank doesn't have to be a daunting task. Once you have done it a few times, it will be fast and easy.

Follow these simple steps to ensure a successful water change and keep your fish happy and healthy.




Gather your supplies.

Before you begin changing the water in your fish tank, make sure you have all the necessary supplies. You will need:

 It’s also a good idea to have a towel nearby to clean up any spills or drips. Make sure all your supplies are clean and free of any contaminants before you start.

Should I Remove my Fish before I Change the Water?

No, moving your fish can lead to stress and will impact their long term health. By changing small volumes aquarium water on a regular basis, there is no need to remove your fish.

Turn off all electrical equipment.

Before you start changing the water in your fish tank, it’s important to turn off all electrical equipment, including filters, heaters. This will prevent any accidents or damage to the equipment while you are working. It’s also a good idea to unplug any electrical equipment to ensure your safety. Once everything is turned off and unplugged, you can begin the water change process.


Clean the Inside of the Glass to Remove Algae from your Aquarium.

Using an Aquarium Safe Scourer, clean the inside of your Aquarium

 Changing the water in a fish tank is an important part of maintaining a healthy environment for your aquatic pets.

To start, it's best to clean the inside glass first to avoid any scraped off algae floating around in the water column. Any algae that is floating about in the water will be siphoned out in the next step or collected through your filtrations system.

Remove old Water and Debris.

The next step in changing the water in your fish tank is to remove the old water Aqua One Lifestyle 29Ltr Aquariumand any debris that may have accumulated in the tank.

Never remove more than a third of the water each month or a quarter every 2 weeks! If you remove any more than this, you risk losing the beneficial bacteria that are in your aquatic eco system.

You can use an aquarium siphon or a gravel vacuum to do this. Place one end of the siphon or vacuum in the tank and the other end in a bucket or sink. Start the siphon or vacuum by sucking on the end that is outside the tank until the water starts to flow. Move the siphon or vacuum around the tank to remove as much debris as possible. Once you have removed the old water and debris, you can move on to the next step.

Clean the Aquarium Decorations.

 After cleaning the inside of your aquarium glass, remove and clean decorations. You don't need to clean every aspect of the tank every time you change the water. Only clean the aquarium decor when it starts to accumulate algae and looks unsightly. This will help keep your fish happy and healthy.

For decorations, remove them from the tank and rinse them thoroughly with warm water. Never use soap or any other cleaning products, as they can be harmful to your fish, just use a scrubbing brush under running water. Once everything is clean, you can move on to the final step of adding fresh water to the tank.

Rinse your Filter media and replace cartridges when Required


Aqua One Filter Brush Double End for Cleaning Aquarium Pipes & Filtration
When changing the water in your fish tank, it's important to avoid deep cleaning your biomedia. This is because the beneficial bacteria that keep your aquarium healthy and balanced live there. To help prevent filter media from blocking up, only ever rinse them in water that has been treated for chlorine. They only need a quick squish about in this water to dislodge anything that is trapped. This will help maintain a healthy environment for your fish without disrupting the delicate balance of bacteria in your tank.


If you are using carbon filters in your aquarium, replace these every 6-8 weeks. The frequency will depend on the number of fish you keep.

Use an aquarium brush specially designed for getting into the pipes of your filter to clean and dislodge any debris and algae.


Add Fresh Water, Conditioner and Aquarium Salts.

Aquarium Salt

Once you have removed the old water and cleaned the tank and decorations, it’s time to add fresh water. Fill a clean bucket with tap water and add a water conditioner to remove any harmful chemicals or chlorine. Follow the instructions on the water  conditioner bottle for the correct amount to add. Slowly pour the water into the tank, being careful not to disturb the gravel or decorations. It’s important to only fill the tank to the recommended level, as overfilling can cause stress to your fish.

Make sure that you add aquarium salt to your water.

Water treatment for Aquariums

Salts are an essential mineral in all freshwater aquariums. Salts assist fish with gill health and function. Follow directions on the packaging and never use table salt as the iodine will be harmful to your fish!

Once the water is added, turn on any filters or heaters and let the tank settle for a few hours before adding your fish back in.

Wipe Down the Exterior Glass of your Aquarium

The final step in the water changing process! Using a microfiber towel, wipe down the outside of your aquarium. Once things inside your aquarium settle you will have a clean viewing aspect to admire your hard work.

Don't forget to check the pH levels after a water change and adjust accordingly.


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