11 Ways to Remove Algae From Aquariums


Algae are microscopic plant-like organisms. Just like plants, they also contain chlorophyll and make their food using photosynthesis. So all the nutrients, light and CO2 that helps plants to grow will also fuel algae growth.

So if you don’t have plants in your tank, it will be easier to control algae. But don’t worry even if you have plants, as we will see how to get rid of algae infestations in a tank.

Before attempting to deal with the algae, it is helpful to know what type of algae it is. Different kinds of algae will require different approaches.

Use These Methods to Remove Algae:

  • Reduce the amount of light available in the aquarium.
  • Reduce the water temperature.
  • Change some of the water regularly.
  • Reduce the quantity of food given to your fish.
  • Test if the water is high in Phosphates and Nitrites.
  • Keep live plants.
  • Keep snails or algae-eating fish.
  • Remove it manually.
  • Use UV Sterilisers.
  • Use a diatomic filter.
  • Use Bleach or Algaecides in extreme situations.

Types of Algae In An Aquarium

1. Brown Algae

This type of algae usually pops up in newly established tanks. It covers the substrate, glass, plants and decorations, but can be wiped off easily with a clean cloth. It doesn’t cause much harm and doesn’t require any drastic measures to remove. It is also called gravel algae or silica algae.

2. Red Algae

This is one of the tougher algae to remove. It usually covers plant leaves. Usually, dipping the infected area in a bleach solution is enough to remove this algae.

After dipping it in the solution, remember to rinse it with fresh, clean water! How to make the solution is mentioned below. It is also called beard algae.

3. Green Algae

This algae doesn’t cause too much harm to the tank. If it is growing in your tank, it is usually a sign that the tank is healthy. However, you don’t want it to overgrow.

Snails and algae-eating fish like Corydoras and Siamese algae eaters readily gobble up this kind of algae. It is also called hair algae, thread algae and spot algae.

4. Blue-Green Algae

This is caused by excess nitrates and / or phosphate in the water. Although called algae, this is actually a colony of a kind of bacteria. It can overpower a tank very quickly and can be difficult to control.

You will need to treat the water to reduce the amount of phosphate and nitrites in it. Erythromycin has been found to be effective against this ‘algae’. It is also called slime algae or smear algae.

5. Green Water

This is also called algae bloom, and is the most unsightly of all algae. It doesn’t grow on walls, substrate or plants, but stays suspended in the water. This gives the tank the appearance of being dirty.

When other types of algae show up, we can simply remove the infected part and treat it. Or if they are on the tank walls, we can remove the fish and equipment and scrub the tank clean. But none of that will help in this case. This makes it the hardest kind of algae to remove.

Partial water changes won’t work, as it grows back very rapidly. Test the water for ammonia, nitrates, nitrites and phosphate, and then treat the water accordingly to reduce all of their quantities.

A noteworthy point is that if you test the water and any of these appear to be within the acceptable range, it is not. It just appears to be ok because the algae is continuously using up all of the nitrates, nitrites, etc. Their content in the water is actually high.

Apart from this, you may need to block all light to the tank, whether sunlight or artificial. Once most of the algae is removed, you can use a diatomic filter to remove any traces of the algae. This will prevent the amount of algae from blowing up again.

Factors that Cause Algae to Grow Rapidly

1. Light

Algae use light for photosynthesis, which they use to multiply rapidly. But we usually cannot cut light supply to our tanks, as the inhabitants need light too. Light is even more essential if there are plants in the tank. 

2. Temperature

Warmer water in the tank aids the algae in growing.

3. Nutrients

Extra nutrients in the tank in the form of excess fish food, too much fish poop and any dead plants or fish will act as a fertiliser for the algae, helping it grow faster.

4. Ph Level

pH levels that are too high or too low can promote algae growth, so monitoring and controlling the pH levels is crucial. You can read how to increase or decrease pH levels in a tank over here.

11 Ways to Remove Algae From Your Aquarium

 Here are 11 ways you can remove algae from your tank. You will need to use 2 or more of these ways together in order to effectively and permanently get rid of algae.

1. Lighting:

Any sunlight entering the tank will ensure that the algae population blooms in your tank. Sunlight will also increase the temperature of the water, making it easier for the algae to grow.

So, no sunlight must be allowed to enter the tank at all. Even the artificial lighting should be restricted. While it is necessary to simulate a day/night cycle in an aquarium, reduce the lighting in tanks without plants to a maximum of 6 hours per day, and a maximum of 8 hours per day for planted tanks.

If you can dim the lights or switch off some bulbs individually, that will also make it harder for the algae to grow further. Also, depending on the type and make of your light bulbs, if they are over a year old, consider replacing them with new ones. Older bulbs actually increase the chances of an algae bloom.

2. Control Food Portions:

Many fish keepers unknowingly feed their fish too much food. When the fish eat more food than they need, they poop most of it out without even using the nutrients in it.

Uneaten food also floats around in the tank or sinks to the bottom. This uneaten food and extra poop greatly impacts the bioload of an aquarium and releases a massive amount of nutrients into the tank. If algae finds its way into your tank when there are so many nutrients, it is sure to grow very fast.

So, it is necessary to only feed your fish what they can consume in under 5 minutes. Any leftover food should be removed.

3. Water Changes:

When any issue related to aquariums is being talked about, water changes have to be mentioned. Usually, a tank will require about a 20% water change every week to keep the water quality in check.

It will also remove any excess nutrients that may have been formed due to the reasons mentioned above. Care should also be taken not to overpopulate the tank.

4. Test Your Water Parameters:

Test your water source periodically to check if it is high in phosphates and nitrites. Checking the pH and hardness is also crucial, as knowing these parameters in your source water will make it easier to increase or decrease them in the tank, if required.

Phosphates and nitrites will be formed in the tank anyway, so if the source water already has them, their levels can spike very quickly and harm the fish. One day you might just wake up and find the fish ‘suddenly’ dead! You can click here to read more on how to increase or decrease the hardness or pH of water.

5. Remove it Manually:

If you see algae growing on the glass, substrate, decorations or anywhere else in the tank, you can simply scrape it off using an algae remover or a razor blade. The scraped off algae will fall on the substrate, so be sure to vacuum the substrate immediately after scraping.

While this method will remove most of the algae, it won’t wipe it out completely, and the remaining algae can grow back quickly. So it is best to combine this with some more methods like a bleach solution or reducing lighting.

6. Keep Live Plants:

Plants and algae use the same nutrients to grow. So if you add plants to the tank, they will compete for the limited amount of nutrients and light in the tank. Healthy plants take up nutrients more efficiently, making it harder for the algae to use nutrients for themselves. This will slow down the growth rate of the algae.

Now that it has become harder for the algae to grow, you can scrape off the visible algae manually and reduce the amount of food given to your fish. If the algae is growing back too quickly, you could even halve the amount of food given for 3-4 days. Doing a large water change will also remove a lot of the nutrients.

7. Keep Algae Eaters:

Once you have brought the algae down to a manageable amount. You could try adding in species that eat algae. The species suitable for your tank will depend on the water parameters like pH and hardness levels, temperature, etc. of your tank.

Keep in mind that adding more inhabitants in the tank will also increase the bioload. Many types of snails are available, the most common being the apple snail. But if you have loaches or assassin snails in your tank already, then it would be pointless to add snails, as they would be eaten. You could also add Ototcinclus catfish or a small variety of Plecostomus.

The commonly available Plecostomus get too large to be kept in a tank, so be sure to research which species you are getting. There are hundreds of small Plecos available, all of which are very beautiful to look at. Apart from these, many species of shrimp are also available, and they will happily gobble up algae.

8. Filter

It is common knowledge that any aquarium of any size needs a filter. But it is helpful to consider the following points: Is the filter in your tank powerful or large enough to efficiently filter a tank of that size? Is it working properly?

Maybe the filter media is full and needs to be cleaned / replaced? Does it have space for biological filtration? (Or, does it have enough space for ‘the good bacteria’ to grow?) Is the water aerated well, so that the biological filtration can do its job properly?

Biological filters break down the nutrients into less harmful nutrients, making it harder for the algae to use them. In particularly bad situations, you may need to get a diatomic filter. Use any number of methods listed on this page to get the amount of algae down, and then use this filter to finish it off.

Diatomic filters are expensive, but filter the water very well. In fact, they are specially made for such situations, and will literally scrub the water clean for you!

9. UV Sterilisers

UV sterilisers emit a beam of ultraviolet light, killing any algae that the light falls upon. However, overexposure will kill or harm any living thing that passes through it, including plants and fish. So they need to be used with caution, and only a few minutes each day should be sufficient. They are also very expensive.

It is better to try the other methods listed on this page first. They will take a few days, but they are worth it. In very bad algae breakouts where nothing else seems to be working, you could get a UV steriliser.

10. Bleach

Another option when the algae covers the decorations or plants is to dip them in a weak bleach solution. Make a solution with 5-10% bleach and 90-95% water. Dip the plants in it for up to 15 minutes, but take care not to let the roots touch the solution.

Decorations can be fully submerged in the solution. Before putting them back in the tank, be sure to rinse the decorations and plants under clean running water.

11. Algaecides

Algaecides are ready-made chemicals that are used to kill algae. They come in the form of liquids, powders or tablets. They are good if you want a quick fix, but the algae can return if you don’t reduce the amount of nutrients and light in the tank. Algaecides can also cause harm to plants and invertebrates, so should be kept as a last resort.

Note On Aeration

Algae use oxygen, just like plants. They also give off carbon dioxide. Both these factors mean that a tank with an algae infestation is very low on oxygen, which can cause you fish to die out.

You should ensure that the amount of aeration (amount of air pumped) in your tank is increased when you notice algae in the tank. It could be increased by using an air pump, powerhead or filter that also pumps air into the water.

Some air pumps come with valves that can be used to regulate the air flow. The flow can be increased if you have these kind of pumps.

Syed Baseeruddin Hyder

I’ve been keeping fish and invertebrates in aquariums for over 5 years. Over the years, I’ve kept more than 15 different species of fish and invertebrates. Through ParadiseInATank.com, I hope to guide new and experienced fish keepers alike with as detailed information as I can get.

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