How to Remove Algae from Fish Tank Decorations?

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While algae aren’t inherently bad in an aquarium, they can become a liability if they overcome the entire environment.

An algae overgrowth will cause a variety of problems by starving plants of their necessary nutrients, lowering the amount of light reaching the lower tank regions, and suffocating the fish.

Dead algae matter can also produce excess ammonia in the water, effectively killing any life form that has survived the algae infestation to that point.

So, you need some reliable prevention and control mechanisms in place to prevent this.

Let’s discuss that!

5 Ways to Remove Algae from Aquarium Decorations

You have 5 primary ways to remove algae deposits from aquarium decorations, given that these are the first to house the emergent organisms.

So, let’s take these, one by one:

1. Scrubbing the Algae with a Brush

This is the first and most natural approach, allowing you to remove visible algae deposits quite effectively.

Get a personalized brush and scrub the decorations thoroughly, especially in harder-to-reach areas where algae are most likely to form. By ‘personalized brush,’ I mean with bristles fitting for the job.

The bristles’ toughness depends on the type of brush and what you’re using it for.

Get one to match your type of decoration. You don’t want a brush with excessively tough bristles that would scratch the piece, remove paint, or destroy the decoration’s structure altogether.

You can brush the decorative piece in a bucket of water that would allow you to clean any algae residues that may stick to it.

Remember to use dechlorinated water or at least allow the clean piece of decoration to dry out naturally for several hours.

You don’t want to transport the chlorine from the tap water into the main tank.

2. Wash Decorations in Hot Water

Boil some water (enough to submerge all of the decorations at once) and submerge the decorations for about 15-20 minutes.

The effect of the boiled water should displace the algae and make it easier to clean even the most stubborn deposits.

Once the 20 minutes have passed, you can remove the pieces from the boiled water and clean them with a brush and some flowing tap water.

The flowing water will eliminate any algae residues more effectively.

Remember the specifications about the chlorine in the tap water, and don’t use any soap or other cleaning chemicals in the process.

These can easily imbed in the material and transfer to the tank water, causing your fish to fall sick.

Also, don’t boil plastic components that cannot withstand higher water temperatures.

Once the plastic is deformed due to the high temperature, it cannot return to its normal form, effectively becoming unusable.

3. Wash Decorations with Bleach

This method is the famous ‘So, you’re at a point where nothing else works, huh?’ strategy.

The thing is that some algae deposits are so stubborn and difficult to remove that you need to go for bleach.

Don’t worry, bleach will evaporate quite fast with a bit of water rinsing and drying. So, it won’t represent a health hazard to your aquarium life.

The cleaning process is similar to the one involving boiling water. First, you prepare the solution. You’re aiming for a solution comprising 5% bleach and 95% water, but you can use a higher bleach concentration if the algae deposits are severe.

Soak the decorations in the solution for approximately 15 minutes. You should notice the algae peeling off after a while as the bleach begins to take effect.

This can last longer, depending on how dirty the decorations are, requiring you to increase the soaking time by up to an hour in many cases.

If you find yourself in that situation:

  • Don’t exceed the recommended 1-hour time limit – The prolonged effect of the bleach may cause the material to lose its coloring.
  • Don’t apply the treatment indiscriminately – The effectiveness and the duration of the bleach treatment depends on the type of decoration you’re using and the material it’s made of. Some decorations cannot withstand prolonged bleach submersion. In this case, a 15-minute submersion session followed by some thorough scrubbing should do the job just fine.

Remember to use a mask and gloves when going for a bleach bath. This toxic and corrosive chemical can cause severe irritations to the skin and any exposed mucous.

The bleach fumes can also reach your lungs for even more problems, in which case the mask is a vital safety component.

Another critical point – only use pure bleach, no additives, colorants, or any perfumes. You cannot know how these artificial additives will interact with the decorations in question.

4. Wash Decorations with Vinegar

Vinegar is another cleaning solution you can use to eradicate algae deposits. The procedure is similar to the bleach one.

First, you create the vinegar solution, which should be 8 fluid ounces to 1 gallon of warm water.

You then submerge the decorations in the solution and let them soak for approximately 5 to 10 minutes. After that’s complete, you remove them from the solution and use a brush to scrub the pieces clean.

Rinse the decorations thoroughly after cleaning to eliminate any visible algae and dirt residues still sticking to their surfaces.

Remember to wear protective gloves and a mask. Vinegar isn’t as intrusive or corrosive as bleach, but it’s still not a chemical you want to inhale too often.

5. Wash Decorations with Hydrogen Peroxide

Hydrogen peroxide ranks as the most effective cleaning and sterilizing solution. It is typically used as a last resort when all other means of sterilization have failed.

Hydrogen peroxide eliminates any algae deposits, along with algae spores, bacteria, viruses, and other microorganisms and pathogens that could infect the water.

Creating the hydrogen peroxide solution is the first and most sensitive step in the sterilization process. To create the final product, you need a 3% hydrogen peroxide solution to mix with water.

The goal concentration depends on the algae you’re looking to combat. If you have a green algae problem, you can use 0.8 to 1 ounce of hydrogen peroxide for every 13-14 gallons of water.

In case of blue-green algae, you only need 0.2 to 0.5 ounces of hydrogen peroxide for the same quantity of water.

If you’re using a smaller container for a handful of decorations, go for 2-3 ml of hydrogen peroxide for each gallon of water.

This is a high-enough concentration for removing any algae deposits and sterilizing the decorations completely.

Now here’s a must-remember closing line: don’t sterilize your tank decorations too often. I understand that algae can become quite the pest in a closed aquatic system, but if they don’t impact the environment too severely, ignore them.

Stick to the brushing cleaning technique rather than resorting to more drastic methods like vinegar, bleach, or hydrogen peroxide.

That’s because these decorations often house billions of beneficial bacteria that consume ammonia and nitrites and turn them into nitrates.

In other words, these microorganisms preserve the system’s chemical and biological balance to create a healthier and more stable habitat for your fish.

Sterilizing decorations, plants, the filtration system, and the tank as a whole too often can sabotage the ecosystem’s stability and viability as a whole.

How to Stop Algae from Growing Back on Decorations?

You’ve asked the right question because prevention is always the better and smarter option.

Fortunately for you, there are quite a handful of algae prevention-and-control methods to consider, such as:

  • Regular siphoning and cleaning – Vacuum the substrate (especially if you have gravel or rocks) and use the siphon to clean any visible algae deposits from your decorations and rock structures. This allows you to remove any young algae before they latch onto the hard surfaces well enough.
  • Mind the nutrients – It’s well-known by now that algae thrive in nutrient-filled waters. This causes them to flourish specifically in aquariums with floating plants that require liquid fertilization. Another problem worth mentioning is the overfeeding aspect. Overfeeding your fish will result in excess food residues, which will feed the ever-expanding algae population. In short, avoid overfeeding, clean lingering food residues, and use liquid fertilization responsibly. You’re looking to keep phosphates below 0.10 ppm and nitrates below 5 ppm. A water tester kit will help you in this sense.
  • Maintain the filter properly – An ineffective filtration system is often linked to algae overgrowth. That’s because a clogged or faulty filtration unit cannot provide sufficient suction power to remove floating particles, food residues, and fish waste effectively. This will create the ideal environment for algae to thrive. Clean your filter regularly and replace sponges whenever necessary to prevent that.
  • Add more plants – If you can, rely on live plants to fill up the space and provide the algae with more competition than they can handle. The plants will consume the nutrients from the water column, starving the algae and preventing them from taking over the environment.
  • Keep the lights low – Algae love high-light conditions. Aquarium plants, on the other hand, don’t. Fish don’t like bright lights either, except for a handful of species. So, there’s really no need to use excessive lighting for your tank, as this will only incentivize the algae to take over.
  • Consider some algae-eating organisms – You have a variety of algae eaters to consider, including fish, shrimp, and different snail species that specialize in algae consumption. Some only eat certain types of algae, while others are more effective in this sense.
  • General maintenance – Finally, there’s nothing more anti-algae than having a good maintenance routine in place. Remember, it’s always easier to clean young algae than deal with their mature versions. Change the water regularly, vacuum the substrate, siphon any detritus deposits, and even scrub the tank walls, decorations, and rocks manually from time to time. The filtration system will suck in all floating algae particles to complete the job.


Algae shouldn’t be a problem in a properly-maintained environment, but this isn’t a universal rule.

Sometimes, these organisms find a way, forcing you to resort to extreme solutions.

Fortunately, I’ve provided you with a few and threw in some good prevention tips to consider along the way as well.

You’re welcome!

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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