Fish & Aquarium

What to do about aquarium algae

If you’re an aquarium owner, chances are you’ll come across algae at one point or another during your aquarium’s life. But what are algae, what do they do, and how does their presence affect your aquarium? Read on below to learn the answer to all of these questions.

What are algae?

Algae, according to science, are a group of organisms that are plant-like and can carry out photosynthesis. This may or may not be totally bad for the environment inside your aquarium – mostly, in nature, algae and marine life live in harmony. However, too much of algae (an ‘algal bloom’) can be dangerous for your fish community, by releasing too many chemicals that can cause a lot of harmful effects, such as nitrates which affect quality of water. Some types of algae are:

Brown Algae

This alga is relatively easy to clean that cover the glass or base of the tank. Methods like scrubs can be used to take these algae off the surfaces of your tank easily.

Blue-Green Algae

This alga can cause a lot of harm to your aquarium and are actually single-celled organisms. A kind of special chemical treatment can be done to kill these algae.

Beard Algae

This alga will only be removed by ridding of affected structures or areas. This is notorious for harming saltwater aquariums and your best bet is using preventive steps.

How do algae affect fish?

Algae thrive on some of the basic components present in an aquarium, e.g. water and light. Sometimes, when the algae in an aquarium are in bloom, they can damage the health of the fish in the vicinity. Because of the increased growth of algae, they can rapidly take up the nutrients and the oxygen dissolved in the water, meaning the fish will be left without the essential components for growth. This could cause death. Other than this:

  1. High amounts of algae can either increase or decrease the pH depending on how they are respiring and what they produce, which will affect your fish.
  2. If you have a saltwater aquarium with corals, the algae can reduce their calcium intake by taking it up instead.
  3. After a bloom, the algae eventually die. This leads to increased nitrogen compounds available in the water, which can be toxic to fish.

How to tackle algae

Once the algae are growing inside your aquarium, you will need to do a couple of things to reduce algal numbers and keep your fish safe from harm. These have been outlined below.

How to tackle algae


When you start out with a new aquarium, it is important to know the kinds of algae that can affect it, its growth, and what measures you can take to stop it from harming your fish. An article like this is a good way to start – prevention is always easier and better than cure.


One way that algal blooms occur is when the aquariums have an excess of light, especially when that light is sunlight. What you can do about this is:

  1. Keep your aquarium out of the sunlight under all circumstances.
  2. Turn off the lights in your aquarium periodically and do not keep them on for a time longer than 8 hours in succession.
  3. You may need to change your bulb as algae show greater growth at lower intensities of light.

If for one reason or another, you can’t maintain a schedule of 8-6 hours of light time, you can use lights with timers in order to keep algae growth at bay.

Maintain water’s quality

As someone running an aquarium, you have the responsibility to keep testing the water and maintaining its quality. This way, a sudden algal bloom (abrupt changes in pH or nitrogen content for example) can be an indicator of poor water quality.


Feeding can be a highlight with an aquarium full of fish, as this is the time where you can see a flurry of activity. According to experts, however, you should only give the fish what they can eat in about 2 minutes of time, to prevent that food from being retained in the aquarium. One key reason for this is that the leftover food acts as nutrients to promote the growth of algae in your aquarium. To prevent this:

  1. Keep an eye on your fish, only feed them what they can eat.
  2. Your fish should eat their food within a couple of minutes.
  3. Try and feed either once a day or in small amounts twice or thrice.
  4. Remove any uneaten food from the aquarium once the fish are done.
Plant competition

Algae are similar to plants so grow in conditions similar to them. If you introduce more plants into the tank, the algae experience ‘competition’. This means that the algae and the plant both want the same things, and so fewer algae will get the resources they need. This will definitely reduce the populations.

Introduce algae-eaters

If nothing else is working, you have another great solution at hand – algae eating fish. All you need to do is introduce them to your tank, and you’ll be rid of your algal problem in no time. Plus, the fish will find a great source of food and grow very well.

High-level Filters

You can also use high-grade filters. These have the ability to remove the excess phosphate and nitrate compounds in the water, which can promote algal growth. Also, after growth of algae, these filters can at least minimize the effect on your fish.

Change water

Another great thing to prevent algal growth is changing the water. And if you have a huge tank that holds gallons of water, don’t worry. All you need to do, according to the people with experience, is to change some percentage of the water regularly.

Scrub them off

It may seem reductive, but sometimes all you can do about algae is to just take it off. Instead of waiting around, adding chemicals into the water, and being extremely or overly careful, you can just scrub off the harmful algae and allow your tank to go back to normal functioning. As you do this though, you need to make sure you remove all of the debris, and that no dead algae are left around to further harm your tank’s fish.

Are all algae bad?

Are all algae bad?

Although the answer to this varies from one aquarium grower to the next, the answer isn’t as clear as it may seem. As someone running an aquarium, you should be wary of algae, but you should also understand that some algal growth may still happen from time to time.

This may not indicate the end of days for your tank, and even though you may consider algae unsightly, they can become a part of your tank’s ecosystem anyway. At the end of the day, algae will provide your fish with nutrients and oxygen, so as long as their concentration is low, they may not be as bad as you think.

Leave a Reply

Your email address will not be published. Required fields are marked *