How to Clean Aquarium Rocks of Algae? Complete Guide

The formation of algae in the fish tank is a sign that the environment inside the tank is typical. But when it becomes excessive, it will cause problems for the aquarium’s inhabitants. Mainly, the formation is quite common on decorative aquarium rocks.

You can clean algae formations on decorative rocks with various chemical solutions. In addition, you can also use water and bleach to wipe out algae completely from the rocks.

But these are only a few of the methods. This article will comprehensively cover most of the well-known techniques to clean aquarium rocks and guide you in the best possible way.

Therefore, let us check it out.

Why Do Algae Form on Decorative Rocks?

Algae formation in the fish tank is inevitable. It can form on the tank glass, plants, gravel, and decorative rocks. Such appearance is normal as light, nutrients, and minerals are provided to the tank, which plays a part in their build-up.

Why Do Algae Form On Decorative Rocks

That said, algae won’t cause any issues if it’s under controlled levels. But without proper planning, that isn’t possible.

Here are some of the main reasons that enhance algae growth:


Lights with higher intensity contribute a lot to algae growth. Generally, artificial lighting is used to dictate the activity of the fish inside. These lighting can be utilized fully when they are used at controlled levels.

In this regard, the optimum time frame for using artificial lights is around 8-10 hours. But if it goes beyond 12 hours daily, there are high chances of algae growth on decorative rocks and surrounding accessories.

Fish Food

Supplements for feeding the fish can be one of the leading causes of algae formation. Fishes need supplements for their growth, but most aquarium owners tend to overfeed the fishes.

Such a tendency eventually gives rise to the phosphate levels in the tank water. As a result, it plays a part in the algae growth in the accessories inside.

Unchanged Water

An aquarium owner must change the aquarium water each week. Changing total volume may not be required, but at least 10-15% of the volume needs to be changed weekly.

Or else, the nitrate level might go high on the tank water, which acts as a plant fertilizer. This element may enhance the chances of plants’ algae growth and decorative accessories like aquarium rocks.

How to Clean Algae from Aquarium Rocks?

You can adopt various methods to clean algae from the decorative rocks on a fish tank. Some of the tried and tested methods are listed below:

How to Clean Aquarium Rocks of Algae

Method 1: Use Bleach

Using bleach is one of the simplest ways to remove the algae, settling down on decorative rocks. Below here are the steps to clean the rocks using bleach:

Step-1: Take the rocks out

A solution like bleach in the fish tank water would kill the fish. Therefore, cleaning the rocks, you first need to take them out.

Take the rocks out to Clean Aquarium Rocks of Algae

Step 2: Put them in a bucket

Take a bucket with a volume of 5 gallons and fill it with water. Then, drown all the rocks in it. While doing so, make sure that the bucket is clean enough.

Put them in a bucket

Step-3: Pour Bleach

Pour the right amount of bleach into the water and let it remain for a week.

Pour Bleach into the water to clean the rocks

Step -4: Check the rocks

Inspect the condition of the rocks after they are dipped in the water for at least a week. If the algae remain, go for 2nd dose.

Check the rocks

Step-5: Apply 2nd dose

Repeat step 3 on the severely affected rocks and keep them drowned again for a week. This step is optional as it is only when the algae don’t go completely.

Step-6: Evaporation

After the rocks are free of algae, keep them in a dry condition for a few days. The reason is to make them free from ammonia, which can harm the fish tank environment.

Evaporation - After the rocks are free of algae, keep them in a dry condition for a few days

Method 2: Use Hot and Colder Water

It is a method that won’t even require any chemical solution. The steps of this method are listed below:

Step-1: Take out the rocks

The first step would be to remove the affected rocks and place them in a clean space.

Take out the rocks

Step 2: Pour hot water

After the rocks are kept separately, pour hot water on them. Carry the whole step a few times by pouring the water slowly so you don’t end up burning your hands.

Pour hot water

Step-3: Pour cold water

Since you have used hot water a few times on the rocks, it’s time to pour some cold water. Just like you did using hot water, repeat this process with cold water for few times. In the end, you will get algae-free rocks.

Method 3: Use Electric Toothbrush

If the algae tint isn’t that severe, it is better to use an electric toothbrush to keep the aesthetics in check. The steps for this process are discussed below:

Step 1: Take a toothbrush

Manage a new electric toothbrush that hasn’t been used before. That said, avoid using a used toothbrush as they might have harmful elements.

Take a toothbrush to Clean Aquarium Rocks of Algae

Step 2: Rub the brush on the rocks

Rub the rocks with layers of algae with the toothbrush. Try rubbing the rocks for at least 4-5 minutes until the algae go off completely.

Rub the brush on the rocks to Clean Aquarium Rocks of Algae


Algae settling down on the surface of the decorative rocks hurts the aesthetics of the fish tank. Not cleaning them can be problematic for aquarium inhabitants. That said, the water becomes cloudy and dirty when you have excessive algae in the aquarium. Therefore, regular cleaning is necessary to keep the algae formation always at a tolerable level.
Some methods involve chemical solutions, while some require only water. You should adopt a single way after inspecting the actual condition of the rock. Moreover, to keep the environment inside the fish tank clean and attractive, you should clean the algae formed regularly.

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