How To Properly Clean A Dirty Fish Tank

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As fishkeepers, keeping a clean fish tank is one of the best ways to care for our aquatic friends.

Keep reading to learn how to clean your fish tank like a pro.

Before You Start…

In order to clean a fish tank, it’s important to know what happens when you don’t clean, how often you need to clean, and the equipment needed to clean a fish tank.

What happens if you don’t clean your fish tank?

Over time, if you don’t maintain your tank and clean it regularly, you could expose your fish to toxic levels of ammonia, along with other chemicals such as nitrites and nitrates. High amounts of any of these chemicals can cause serious harm to your fish. 

To limit the amount of toxic chemicals, beneficial bacterias grow inside your tank to eliminate them through the nitrogen cycle. But as water gets dirtier, these bacterias start to die off causing your fish to become vulnerable and your tank to look grimy.

A good sign to clean your tank would be if your fish aren’t eating enough, become discolored, display decreased energy levels, or appear to get sick. If you don’t clean your tank soon enough, your fish could even die!

How often should you clean your fish tank?

Some people say you should clean your tank once a week, while others say once a month. All tanks are unique so the real answer is that it depends! 

Some factors that determine how frequently you should clean are the size of your tank, how many fish you keep, and how much biological filtration(e.g beneficial bacteria and live plants) you have.

For those that want to replicate what I do, I change the water in all my tanks every 2 weeks. I’ve found this to be the sweet spot for many community tanks.

Equipment Checklist

Now that you understand the importance of cleaning your fish tank and you’re ready to start cleaning yours, we’re going to need a few simple cleaning supplies to get your aquarium in shipshape again.

What You’ll Need

  • Bucket (New and for aquarium use only)
  • Paper Towels
  • Algae Scraper
  • Razor Blade (Plastic blade for acrylic tanks)
  • Bleach
  • Water Siphon (Gravel Vacuum)
  • Aquarium Glass Cleaner
  • Filter Media
  • Filter Brush
  • Chlorine Remover (Aquarium Water Cleaner)

Cleaning the Fish Tank

Now that you know what you need to keep your tank clean, the following guide is for how to clean a fish tank. It’s important to follow each step in the following order.

Step 1: Clean the Interior Glass

Use an algae pad or scraper to clean the glass on the inside of the tank. There’s a variety of different scrapers or pads out there that you can get. For those with larger tanks, you might want to opt in for scrapers with long handles to make it easier to reach the inside.

When purchasing an algae scraper, make sure to get it at a pet store rather than a department store. Algae scrapers designed for fish tanks wont contain any of the harmful chemicals that can hurt your fish.

If you use a scraper or pad but still notice any residue remains, you can use a razor blade to remove the residue. For acrylic tanks, only use a plastic blade to avoid damaging the glass.

Smart Fishkeeping Tip: Use a magnetic algae scraper to clean your tank. Using one will be easier because they stick to the glass.

Step 2: Clean all Rocks, Plants, and Other Decorations

After you’re done cleaning the interior glass, remove all decorations, rocks, and plants from the tank that are visibly dirty. Never use soap to clean any of the decorations. Even if you rinse thoroughly, small particles of soap will still appear causing harm to your fish. Instead, use an algae scraper to get the job done.

If you can’t clean your decorations with an algae scraper, create a 10 percent bleach cleaning solution and let the decorations sit in it for 15 minutes. Once you’re done soaking them, be sure to wash any additional grime off and let them air dry until the bleach is completely removed.

For cleaning plants, use a 5 percent bleach cleaning solution and let them sit in it for 3 minutes. The only plants you shouldn’t bleach are stem plants because you can damage their roots through bleaching. Make sure any plants getting bleached are thoroughly rinsed before getting added back into the tank.

Also, wait until you have washed the gravel before adding any decorations or plants back into the tank to ensure a thorough cleaning. 

Smart Fishkeeping Tip: Have a bucket used only for cleaning the tank. This will help you avoid contaminating the tank.

Step 3: Clean the Gravel with a Siphon

This step involves “vacuuming” the debris from the gravel using a Siphon. It really doesn’t matter which type of siphon you decide on using, but the main function of it should be to remove debris from the gravel without actually removing the gravel from the tank.

Make sure to replace any water lost during the gravel cleaning process with dechlorinated water. Always use tap water as this will give your fish vital nutrients purified water won’t. 

Always make sure that the temperature of the water you’re adding is close to the temperature of the aquarium’s water. A human finger can detect temperatures within 1-2 degrees so “feel out the water” until both feel the same.

When replacing water, turn off your aquarium’s heater to prevent contamination from the air.

Step 4: Clean the Exterior Glass and Fixtures

With the interior of the tank cleaned it’s time to focus on the exterior. When cleaning the exterior of the tank, you should include the tank’s glass, hood, top, lights, and any other fixtures. When cleaning, stick to vinegar or another type of cleaner intended for use on aquarium glass.

Step 5: Clean the Filter when needed

After you’ve cleaned your tank, wait about two weeks before cleaning the filter. The reason for this is because your filter contains beneficial bacteria that are lost during the cleaning process. By not cleaning your filter, you’re allowing it to give back those bacteria to the tank. Cleaning the filter too soon can cause chemical buildup deadly to the health of your fish.

When cleaning your filter, you should replace any media with ammonia absorbers, ion-exchange resins, or carbon. Also make sure to clean every part of the filter, including the tubing.


Now that you know how to clean your tank, it’s important to stay consistent. Stick to a strict schedule of when to clean your tank and replace the media inside your filter.

Always make sure that any equipment you decide on using for cleaning your tank should only be used for cleaning to prevent contamination.

With a successful cleaning habit for your tank, you can now look forward to crystal clear waters with happy, healthy fish!

Photo of author
Hey there, my name is Gunnar Kennedy. I'm a fishkeeping enthusiast who's been in the hobby for over a decade now! I love sharing new ideas and helping others care for their aquatic friends!

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