How to Clean a Fish Tank

Saifullah Ashrafi

Keeping a clean fish tank isn’t just about making it look good—it’s about ensuring the health and happiness of your fish. With the right tools and a regular cleaning routine, your tank will thrive, and your fish will swim around in a healthy environment. Let’s start with an easy to follow guide to properly clean your fish tank.

1. Start With Clean Hands

Before you get started, wash your hands thoroughly to avoid introducing any harmful bacteria into the tank. Even trace amounts of soap, oils, or lotions can negatively affect your fish’s delicate ecosystem.

2. Turn Off the Electronics

To avoid any electrical issues, turn off your filtration system, heater, and lighting. Your fish will be safe without these for a short period, and it ensures you don’t risk shocking yourself or damaging the equipment.

3. Remove and Clean Decorations

Carefully take out all decorations from the tank and place them in a bucket or on a towel. Using a scrub brush (or an old toothbrush), clean off any algae or debris from the décor. Make sure you only use this brush for aquarium purposes to avoid contamination.

4. Scrub the Tank Sides

Next, use a scrub brush suitable for your tank material—whether it’s acrylic or glass. Gently scrub the sides of your tank to remove algae buildup.

5. Vacuum the Gravel

Using a siphon, vacuum the gravel to clean up waste, leftover food, and debris. To do this:

Place the siphon in the tank and get the water flowing into a bucket.
Move the siphon around the tank, pulling up some gravel with it.
Let the gravel settle, and lift the siphon to move to the next section.

By doing this consistently, you’re keeping the substrate clean and ensuring better water quality for your fish.

Pro tip: Be patient—vacuuming is a learning curve but gets easier with practice.

6. Rinse the Filter Media

After you’ve vacuumed, take out the filter media (sponges, floss, etc.) and rinse it in the dirty water you siphoned out. This keeps the beneficial bacteria intact, which is essential for your tank’s nitrogen cycle. Don’t replace the filter media unless it’s falling apart.

7. Prepare Fresh Water

Now, fill a bucket with fresh tap water. Use a thermometer to check the temperature, ensuring it matches your tank’s water. This prevents your fish from going into shock due to sudden temperature changes. Add a water conditioner to neutralize harmful chemicals like chlorine. For saltwater tanks, mix in the appropriate amount of salt, and let it circulate for a few minutes.

8. Slowly Refill the Tank

Slowly pour the fresh water into your tank, making sure not to disturb your fish too much. This gradual process keeps your fish calm and prevents the tank from getting cloudy.

9. Turn Everything Back On

Once your tank is refilled, turn on the lights, heater, and filtration system. If necessary, refer to the manufacturer’s instructions to prime the filter for proper functioning.

10. Wash Your Hands Again

Finally, give your hands another wash to remove any tank residue. This is an important step in how to clean a fish tank.

How Often Should You Clean Your Fish Tank?

Regular cleaning is vital to keep your fish tank healthy. However, the frequency depends on several factors like tank size, number of fish, and filtration. In general, it’s recommended to replace 10% of the water weekly or 25% every two weeks for most established tanks. New tanks might need more frequent attention due to the incomplete nitrogen cycle. Testing your water parameters regularly can help you determine when cleaning is necessary. Pay close attention to your tank’s ammonia levels (keep them under 0.25 mg/L), nitrite (should be at 0 mg/L), and nitrate (below 20 mg/L). If these levels spike, it’s time for a water change, as poor water quality can lead to stressed or sick fish.

Never remove more than 50% of the tank’s water at once. Doing so can cause abrupt changes in water chemistry, stressing your fish and disrupting the tank’s equilibrium. Gradual water changes are always preferable for maintaining stable conditions.

Should You Take Fish Out During Cleaning?

No, you should not take your fish out of the tank during regular cleanings. Moving them causes unnecessary stress, which can weaken their immune systems and make them more susceptible to disease. When cleaning is done properly, your fish won’t be bothered by the process. The gentle scrubbing of the tank sides, vacuuming of the substrate, and water changes should be slow and steady, ensuring that your fish remain calm.

The only exception is when you detect hydrogen sulfide in the substrate (signaled by a rotten egg smell). This indicates that the substrate is releasing a toxic gas due to bacterial decomposition in areas where there is no oxygen. If this happens, you’ll need to perform a deep clean and remove the fish temporarily to a holding tank with their filtration system. Once you’ve removed the toxic substrate and replaced the water, your fish can safely return to their home.

Key Tools You Need for Tank Maintenance

Water Quality Test Kit: This kit allows you to monitor crucial water parameters like ammonia, nitrite, nitrate, and pH. Regular testing ensures you can act quickly before harmful levels affect your fish. Some kits also test for chlorine, hardness, and alkalinity.

Algae Scrubber: This tool is used to scrape off algae from the walls of the aquarium. Make sure to use a scrubber that matches your tank’s material—softer scrapers for acrylic and harder ones for glass—to avoid scratching the tank surface.

Refractometer (For Saltwater Tanks): A must-have for saltwater aquarium owners, this tool checks the salinity level of your water. Maintaining the correct salt levels is critical to the health of your marine tank.

Gravel Siphon: A siphon helps remove debris and waste from the tank’s substrate. It effectively vacuums the gravel without disturbing your fish too much. Learning to use one may take practice, but it’s a vital tool for maintaining a clean environment.

Thermometer: A thermometer helps ensure the water you add during a water change is the same temperature as the tank water, which prevents temperature shock for your fish. Infrared thermometers are quick and reliable for spot-checking water temperatures.

Tap Water Conditioner: Essential for treating tap water, it neutralizes chlorine and chloramine, which can be harmful to fish. A conditioner keeps your water safe, preventing the buildup of toxic chemicals.

Freshwater vs. Marine Tank Cleaning

Cleaning freshwater and marine (saltwater) tanks involves similar steps, but marine tanks require more precision and attention to detail. While freshwater tanks are generally easier to maintain and tolerate slight fluctuations in water chemistry, marine tanks need careful monitoring of salinity, pH, and other parameters to support delicate marine life, including corals and invertebrates. Marine aquariums often house live corals, which are sensitive to changes in water conditions, so you must regularly check and maintain salinity levels with a refractometer.

Additionally, the cleaning process for marine tanks involves extra caution when vacuuming near corals and live rock to avoid disturbing these sensitive structures. Saltwater tanks also produce more organic waste, so filtration systems and protein skimmers require frequent attention to keep water quality high.

Health Precautions

Fish tanks can harbor zoonotic diseases, like mycobacterial infections that cause non-healing skin lesions. Always avoid tank water if you have open cuts, and keep children or those with compromised immune systems away from handling the water.

By following these steps, you’re not just maintaining a clean fish tank but creating a healthy environment where your fish can thrive. Regular care means a happy and vibrant tank for years to come.