Ebb and Grow: Growing and Controlling Algae in Your Aquarium

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Having a little bit of algae in your freshwater tank is generally not a problem but, if you aren’t careful, a little bit of algae can quickly turn into a lot. Algae is just like any other living thing – it requires certain conditions and specific nutrients in order to grow. If you learn what those requirements are and how to control them, you can effectively keep your algae under control as well.

Things Algae Needs to Grow

If you think of algae in similar terms to aquarium plants, you will find it much easier to understand. Like aquarium plants, algae needs light and nutrients in order to grow – it also requires water and carbon dioxide. If any of these things is available in your tank in excess, there is a greater likelihood that your tank will develop an algae problem. Here’s an overview of each of these four essential algae elements:

Light: Like live plants, algae requires light in order to grow. Algae uses photosynthesis (just like plants) to convert light into energy. Unlike plants, however, algae does not produce leaves that are used to absorb the light – algae are photoautotrophic organisms that convert light directly into energy.

Related: What Causes pH Changes and How to Fix Them

Nutrients: Algae requires a number of different nutrients in order to thrive, but there are two that are most important – nitrogen and phosphorus. While live plants typically gather nutrients from the substrate in your tank, algae can absorb nutrients directly from the tank water. The amount of nutrients available to algae in your tank depends on the amount of organic waste and debris – overfeeding your fish or failing to perform water changes can lead to an excess of nutrients which will support algae growth.

Carbon Dioxide: Similar to live plants, algae converts carbon dioxide into materials that it can use. Oxygen is a byproduct of this process, though algae doesn’t produce as much oxygen as live plants do. High levels of carbon dioxide may support rapid algae growth, so be careful when adding supplementary CO2 to your planted tank.

Water: The final thing algae needs to grow and thrive is water – this is available in abundance in your tank. You cannot reduce the amount of water in your tank to prevent algae growth because your plants and fish also need that water to thrive. You can, however, control the temperature of the water and use weekly water tests to make sure that water chemistry remains stable.

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Tips for Controlling Algae Growth

Now that you have a deeper understanding of what algae needs to grow in the freshwater tank you will be better equipped to control algae growth. The simplest thing you can do to control algae growth in your tank is to limit your tank lighting. If you place your tank near a window that gets a lot of direct sunlight you will be fighting a constant battle against algae. Even aquarium lighting that is too bright, or lights that are left on too long, can contribute to algae growth. Make sure not to keep your tank lights on for more than 10 to 12 hours and do not use high-intensity lighting unless you have a lot of plants.

Another factor in controlling algae growth involves controlling the availability of nutrients. When you feed your fish they produce waste which accumulates at the bottom of your tank along with any uneaten fish food. As that waste decomposes it produces nitrogen and phosphorus, among other things, which algae can use for growth. To control algae growth you should avoid overfeeding your fish and make sure that your tank water stays clean.

It doesn’t take long for a little bit of algae to turn into a full-on algae bloom. The more you know about aquarium algae and how it grows, the better you will be able to control it in your own aquarium.