Why Decorations in Your Fish Tank Are Turning Brown

By Eddie Waithaka @aquariawise

How to Remove Brown Algae from Fish Tank (+Decorations)

Aquarium decorations are one of the main attractions of any fish tank, and it can be depressing when they start to turn brown.

There are a few reasons why this might happen, and luckily there are also a few ways to fix it.

Aquarium decorations and plants turn brown due to a build-up of brown diatomic algae following increased organic material, especially in new tanks. Another possibility is that the decorations are made from a material slowly dissolving in water.

If this is the case, you may want to switch to a different type of decoration.

Wet driftwood may also release tanning in an aquarium and cause your water and decoration to look brownish.


In this blog post, we’ll look at these and other items that might be causing your aquarium decorations to turn brown and how you can restore them.

Just keep reading!

What Causes Brown Algae in Aquarium Decorations

As noted above, brown algae is the most likely reason decorations are turning brown in your fish tank.

But where do brown algae come from?


There are many potential causes of brown algae in fish tanks, but the most common cause is excess light and nutrients, such as phosphates and nitrates, in aquarium water.

In turn,…

These nutrients are caused by several conditions, including overfeeding, dirty filters, and too much aquarium light for many hours. Other causes can include poor water circulation and too much carbon dioxide in the water.

With zero live plants to outcompete the algae for light and nutrients or algae-eaters to consume some of the algae, brown diatoms will gradually develop from your substrate to your decorations and even on your fish tank glass.

How to Remove Brown Algae from Fish Tank (+Decorations)

Brown, unsightly algae can be difficult to remove, but with some know-how, it can be done in a few simple steps.

1.Clean your tank. This is the first step in getting rid of brown algae. Ensure you remove all the algae from the tank and any organic debris, such as fish waste, decaying plants, and leftover fish food.

2.Add an algae eater. We have several fish in the hobby that eat algae, and adding one to your tank can help remove brown algae. If you have a tiny tank, consider getting small non-fish species, like dwarf Amano shrimp and nerite snails or fish, like dwarf suckers. Note that most fish prefer green to brown algae and will feed on it more if there is some in your fish tank.

3.Reduce aquarium lighting. Brown algae seem to thrive in a high-light environment, so turning off your fish tank lights several hours a day may help reduce or discourage more algae growth. You may also want to move your fish tank away from windows.

4.Remove Nutrients from the fish tank. Excess phosphates, nitrates, and high light will help algae thrive in your fish tank and on decorations and plants. Adding live plants in your fish tank to consume the excess nutrients will help starve the brown algae.

5.Remove uneaten food and decaying plant matter regularly. Nutrients that brown algae consume in a fish tank come from organic waste, so one of the best ways to remove the algae is clean this waste regularly. Try to yank out brown algae growth from the substrate, glass, and decoration, while removing fish waste and uneaten food from the tank.

6.Add Heavy Feeding Plants. If the biological environment in your fish tank can support heavy plant growth, add plants like cryptocoryne and amazon swords, and vallisneria to compete for nutrients with the brown algae.

7.Reduce Carbon Content. Injected C02 in a fish tank is used to help heavy-feeding aquarium plants thrive. However, too much CO2 will boost brown algae growth, especially in new setups.

How to Stop Brown Algae from Growing in A Fish Tank

So, what can you do to stop brown algae from growing in your fish tank?

Well, most hacks that will remove brown algae will also keep it from growing back.

Here are a few tips:

1.Make sure you’re not overfeeding your fish. Excess food can lead to algae growth.

2.Ensure your tank is well-lit, but avoid direct sunlight and keep the lights on only for the recommended period. That is between 8 and 12 hours daily.

3.Clean your tank regularly. A clean tank is less hospitable to algae growth.

4.Add an algae eater to your tank. Algae eaters can help keep your tank clean and algae-free.

5.Add live plants to your fish tank to outfeed and starve the brown algae in your fish tank.

6.In new fish tanks, you may not need to do anything to stop brown algae growth. The pesky little algae will fade out once the aquarium environment stabilizes.

If you follow these tips, you should be able to get rid of brown algae for good!

How to Remove Brown Algae from Aquarium Decorations

Once you’ve addressed the underlying cause of the brown algae on your fish tank decoration, you can start to remove it. A simple way to do this is to scrub them with a toothbrush.

You can also use a commercial algae-removal product or try a home remedy such as vinegar or baking soda.

Soak your decorations in the baking soda and vinegar solution overnight to loosen the brown algae build-up, then go in with a toothbrush the following morning to clean it off.

No matter the method, ensure you rinse the decorations thoroughly after cleaning them. This will help remove any remaining algae and prevent it from growing back.

How to Remove Algae on Aquarium Glass

Sometimes you will notice brown algae develop on your aquarium glass. Fortunately, removing algae from aquarium glass should not be too tasking.

You can try scrubbing it off with a sponge or toothbrush. If it is tightly stuck on the glass, try using an algae scraper or a razor blade. Be careful not to damage the glass.

You can also try adding an algae eater, including shrimp and snails, to your aquarium. These fish will eat the brown algae on decorations and glass walls and help to get rid of it.

Finally, make sure to keep your tank clean and well-maintained. This will help prevent brown algae from developing in the first place.

Is Brown Algae Bad for Fish

Brown algae is not bad for fish. It is a natural part of some fish’s diet and provides them with essential nutrients.

However, too much is not ideal for a home aquarium environment. So, it helps to monitor the amount and keep it in check.

That’s all for this post. We hope the read was informative!

← All articles

The Aquarium Club ↓

Join the 37k+ strong aquarium community

The AquariaWise Newsletter is known for cutting through the noisy world of pet fish keeping showcasing stunningly breathtaking aquarium fish and superbly insightful aquarium plants to help you bring out the peace and serenity you seek with your aquariums. And it doesn't stop there... think aquarium fish care, plant care, building fish tanks, everything aquariums... you'll be right at home.