Low-tech aquariums How to Easily Control Algae in Low-Tech Planted Aquariums

How to Easily Control Algae in Low-Tech Planted Aquariums

Algae is beneficial for regulating nutrients, providing oxygen, and acting as a food source for fish and fry. But too much algae can be a problem. You can prevent algae by reducing light intensity and duration, minimizing excess nutrients, reducing CO2, and adding more plants to compete for resources.

Understanding the factors affecting algae growth and how they interact with the aquarium ecosystem can help in maintaining a clean and thriving aquatic environment.

This resource will provide you with a better understanding of algae’s role in your low-tech aquarium.

Photo of aquarium with green algae

How to Get Rid of Common Aquarium Algae

Different types of algae can occur in aquariums, each with unique characteristics:

Algae typeDescription of algaeHow to get rid of it
Green algaeAlso known as green water, this type of algae results in a greenish tint in the water due to the presence of floating, unicellular algae.Reduce excess nutrients & overfeeding
Blue-green algaeOften mistaken for algae, cyanobacteria is technically a type of bacteria capable of photosynthesis. It forms slimy, blue-green sheets on surfaces and can produce a foul smell.Lower light exposure
DiatomsBrown algae that commonly appear in new aquariums, diatoms grow in the presence of silicates and nitrates.Clean surfaces & minimize excess nutrients
Green spot algaeSlow-growing, hard, green spots that typically appear on tank surfaces.Reduce CO2, phosphate or nitrate levels
Black beard algaeA type of red algae known for its black tufts resembling hair.Increase CO2 and maintain consistent light schedule
Staghorn algaeA greyish-green, branched filamentous algae that can resemble deer antlers.Increase CO2 and maintain consistent light schedule
Thread algaeLong, thin green strands that can attach to and grow on plants.Outcompete with higher plant density or lower excess nutrient levels

Being aware of the different types of algae that can grow in an aquarium, along with their unique characteristics, can help me create a balanced and healthy environment for my low-tech planted tank.

Proper prevention and control methods will ensure minimal algae growth while maintaining the beauty and vitality of my aquarium.

What is Algae and How Does it Grow?

Algae is a diverse group of photosynthetic organisms, ranging from unicellular microalgae to multicellular giants like kelp. They often inhabit various low-tech planted tanks and can be considered a common issue for aquarium owners.

However, almost all algae species are harmless and are considered undesirable merely because they make aquariums look “unclean.”

Aquarium algae and aquatic plants require many of the same nutrients to grow. They both need macronutrients such as carbon (C), nitrogen (N), and phosphorus (P), as well as a range of micronutrients like iron (Fe), magnesium (Mg), potassium (K), and others.

Both algae and plants use these nutrients for photosynthesis and other essential metabolic processes. However, one of the key differences between the two is their adaptability and efficiency in nutrient uptake.

According to Fordham University, the distribution of algae in an aquarium or other freshwater environment are also influenced by the water’s salinity, depth, transparency, and pH, among other things (Wehr, 2003)[1].

Also, certain algae, such as Cyanobacteria, are most common in freshwater environments, while others, such as diatoms, are more common in marine environments[1].

Algae are generally more efficient than higher plants at utilizing nutrients, particularly when these nutrients are in abundant supply. This is why over-fertilization or overfeeding in an aquarium can often lead to algal blooms.

Many aquarist might not realize that algae plays a crucial role in their aquarium ecosystem, contributing to oxygen production and nutrient cycling. They also provide a food source for certain types of fish and invertebrates

In low-tech planted tanks, where carbon dioxide injection is absent, algae control can be challenging but achievable. The main concern is having abundant algae growth that outcompetes your other aquarium plants for nutrients.

Role of Algae in Aquarium Ecosystems

As someone who has worked with aquariums for years, I believe it is crucial to consider the role of algae in low-tech planted tanks. In this section, I’ll discuss the benefits of algae, problems caused by algae, and cover relevant topics, such as beneficial bacteria, oxygen, algae outbreaks, and algae control.

Benefits of Algae

Algae, a diverse group of photosynthetic organisms, play a key part in aquatic ecosystems:

  • Nutrient Regulation: Algae can help balance nutrient levels in your tank by absorbing excess nitrates, phosphates, and carbon dioxide. This can be especially beneficial in overstocked tanks or those with less efficient filtration systems.
  • Oxygen Production: Like all photosynthetic organisms, algae produce oxygen as a byproduct of photosynthesis. This can help increase the oxygen levels in your aquarium, benefiting your fish and other aquatic inhabitants.
  • Food Source: Certain types of algae, like spirulina, serve as a nutritious food source for many fish and invertebrate species. Algae can provide a variety of essential nutrients, including vitamins, minerals, and proteins.
  • Aesthetic Appeal: While this is subjective, some aquarists appreciate the natural look that certain types of algae can provide. For instance, Marimo moss balls are a type of algae that are often used for their appealing appearance and ease of care.
  • Beneficial for Fry: Algae can also be a good microhabitat for fry (baby fish) as they provide cover and a source of infusoria (small aquatic creatures) which the fry can eat.

In low-tech planted tanks, healthy amounts of algae support a balanced ecosystem that allows fish and plants to thrive. It is essential to understand that some presence of algae is natural and plays a beneficial role.

Problems Caused by Algae

Despite the benefits, excessive algae growth, also known as nuisance algae or algae outbreaks, can cause several problems in the aquarium ecosystem:

  • Competition for Nutrients: Algae compete with aquatic plants for light and essential nutrients. When algae proliferate, they can starve plants of these vital resources, inhibiting their growth and overall health.
  • Blocked Light: Dense algae growth, especially on the surface of the water, can block light from reaching the plants and other algae species in your tank, inhibiting their ability to photosynthesize effectively.
  • Oxygen Depletion: While algae produce oxygen during the day, they consume it at night. In cases of severe overgrowth, they can deplete oxygen levels during the night, potentially stressing or harming your fish.
  • pH Swings: Algae absorb carbon dioxide (CO2) during the day, which can cause a rise in pH, and then produce CO2 at night, leading to a drop in pH. This can result in significant pH swings, which can be stressful or even harmful to your aquarium inhabitants.
  • Difficulty to Remove: Some types of algae, like black beard algae or green spot algae, can be particularly stubborn and difficult to remove once established.

Remember, the aim is not to eliminate algae completely but to keep its growth in check so that it continues to play its beneficial role in the ecosystem.

Conditions Promoting Algae Growth

Lighting and Algae Growth

In my experience, lighting plays a significant role in algae growth in low-tech planted tanks. Algae, like plants, need light for photosynthesis. When there’s an excess of light or if the lights are left on for too long, it can promote algae growth.

Also, carbon is a more scarce resource in low-tech tanks because it’s not beign artificially injected in. As a result, your plant will not be able to efficiently use the liht energy, which improves the opportunity for algae to grow.

To maintain a balance, I usually adjust the intensity and duration of the light exposure. I either buy tanks with a timer built in, like my HICREW:

If my lights do not have a built-in timer then I will connect them to a power on/off timer and sjust it to run for 8-10 hours per day on low-medium intensity:

GLO automatic light timer

Nutrients and Algae Growth

Another factor I’ve noticed that encourages algae growth is the abundance of nutrients in the tank, such as nitrogen, phosphorus, and potassium. To reduce the possibility of excessive algae growth, I’ve learned to manage the balance of nutrients in my low-tech tank.

A study from the University of Bristol discovered a pattern between algae growth and the availability of nitrate, phosphate and silica (Round, 1972)[2].

Where do these nutrients come from?

  1. Nitrates: The primary source of nitrates in an aquarium is the nitrogen cycle. Fish excrete waste in the form of ammonia, which is then converted to nitrites by beneficial bacteria. Another type of bacteria converts these nitrites into nitrates. Overfeeding your fish or having too many fish in your tank can increase the amount of nitrates.
  2. Phosphates: Phosphates often enter the aquarium through fish food. Most fish foods contain phosphorus, which is an essential nutrient for fish, but any uneaten food or fish waste can contribute to phosphate levels in the water. Overfeeding can exacerbate this. Phosphates can also be introduced through tap water and certain types of aquarium substrates and decorations.
  3. Silica: Silica often comes from tap water or well water, though it can also be introduced through certain types of substrates or rocks that contain silicate minerals. Certain salt mixes used in saltwater aquariums may also contain silicates.

The point is not to try completely eliminating these nutrients, because that’s nearly impossible to do. Rather, choose not to worsen the problem by uncecessarily adding these nutrients to your tank.

The biggest mistake I used to make was adding too much liquid plant fertilizer to the water column.

I used to believe that fertilizer was necessary to provide my plants with enough nutrients. What I’ve learned is that they receive more than enough nutrients from my organic dirt substrate an decomposed organic material.

My dirted 20-gallon aquarium

If you don’t add supplementary nutrient (i.e. fertilizers), it will be difficult to create algae blooms as a result of nutrient abundance.

This doesn’t mean you won’t have algae. There may be other sources of excess nutrients or other factors (such as too much light) that are causing your algae problems.

Algae Prevention in Low-Tech Planted Tanks

Correct Lighting

To minimize algae growth in my low-tech planted tank, I ensure that the aquarium receives the appropriate amount of light. I aim for around 8-10 hours of light daily, as excessive light can cause algae blooms.

Additionally, I use high-quality LED lights that mimic natural sunlight, providing the necessary spectrum for plant growth without promoting algae proliferation.

Proper Nutrient Balance

Maintaining proper nutrient levels in my aquarium is essential for the health of my plants and preventing algae growth. I test my water regularly for nitrate, phosphate, and potassium levels and strive to maintain the following parameters:

  • Nitrate: 10-20 mg/L
  • Phosphate: 0.5-1 mg/L
  • Potassium: 8-15 mg/L

Water movement

Adequate water circulation ensures that nutrients in the water are evenly distributed throughout the tank. This allows all plants in the aquarium to access the nutrients they need to thrive, thereby outcompeting algae for these resources.

Without adequate water movement, certain areas may become nutrient-rich “hot spots,” which can promote localized algae blooms.

I use a low-power powerhead at the bottom of my aquarium to circulate water



  1. Wehr, J. D. (2003). Freshwater habitats of algae. Freshwater Algae of North America-Ecology and Classification, 11-57.
  2. Round, F. E. (1972). Patterns of seasonal succession of freshwater epipelic algae. British Phycological Journal, 7(2), 213-220.

Ryan Ferguson

Founder, Rooted Tank

Ryan Ferguson, the founder of Rooted Tank, started fishkeeping in 2019. He has continued to level-up his planted aquarium skills and wanted to share his journey and knowledge with other aquarists.



227, 25 Auburn Meadows Avenue SE, Calgary, Alberta, Canada, T3M 2L3