Does Algae Stunt Aquarium Plant Growth?

4 min read

Getting your aquarium conditions just right can be challenging. You’ll need to ensure the water in the tank is of the appropriate composition for your plants to get the nutrition they need. So when algae appear in your tank, it’s easy to understand why you’d want to be proactive in getting rid of them.

Algae stunts aquarium plant growth. It blocks light and deprives your plants of carbon dioxide and nutrients. Additionally, it can impact the pH levels of the water in your tank. If left unchecked, algae will not only stunt your plants’ growth; it will eventually kill them.”

In this article, I’ll explore the risks of unchecked algal growth in greater detail and let you know how you can control the algae in your aquarium tank.

Risks of Algae in Your Aquarium

Greenalgae01 PetAquariums Does Algae Stunt Aquarium Plant Growth?

Many tank owners are aware that algae have their benefits. Several species of aquarium fish, including cherry shrimp and guppies, enjoy eating algae. Additionally, some people like the look of algae in an aquarium tank. Given these pros, you may wonder why you need to get rid of algae at all.”

If you don’t have plants in your aquarium or have a balanced tank with algae-eating fish, you may not need to remove or even control algal growth. However, things change when you have a tank with several varieties of marine plants or don’t have enough algae-eating fish.

Some of the risks of algae growth in your aquarium include:

Stunted Plant Growth

As mentioned above, algae rob your aquarium plants of CO2 and nutrients essential for their proper growth.”

This is because, as it grows, algae spreads over the surface of the tank water, positioning itself so it can access CO2 and any available nutrients first. In doing so, it also blocks light from reaching your plants, further restricting the resources available for their growth.”

If algae are left unchecked, your plants will eventually starve to death.

Adverse Fluctuations in pH Levels

In large quantities, algae have a uniquely adverse impact on the pH levels of the water in your aquarium.”

Like other plants, algae photosynthesize during the day. This means that they absorb CO2 for photosynthesis during the day. Over time, the lower levels of CO2 in the water of your fish tank can cause its ph levels to rise.”

However, at night, algae stop photosynthesizing but continue to respire. Plant respiration (including that of algae) is similar to human respiration – they take in oxygen and “exhale” CO2. Because there is no intake of CO2 to offset this respiration, the CO2 levels in your tank’s water will rise, and its pH levels will drop.

In a healthy aquatic ecosystem, this isn’t a cause for concern. However, an overgrowth of algae in your tank can cause severe swings in the tank’s pH level. Depending on which plants you have in your aquarium, this can affect plant growth.”

Most aquarium plants – and fish, for that matter – require a specific pH range to thrive. This pH range differs depending on the plant, and some plant species can tolerate a broader range of fluctuation than others. If your aquarium plants are sensitive to pH changes, the change in pH levels due to algal respiration can adversely affect their growth.

The high pH levels during the day in cases with excess algal activity also result in higher ammonia levels in the water. High ammonia levels can harm aquarium fish and plants and eventually can kill them.

Getting Rid of Algae in Your Aquarium

Clearing your tank of algae altogether is almost impossible. Algae form when nutrients and the lighting in your tank are imbalanced, and getting the balance perfect is nearly impossible. 

However, it is possible to eliminate excess algae and ensure minimal algae growth. Some steps you can take include:

  • Controlling lighting. Too much light promotes algal growth, and sunlight, in particular, increases the growth rate of algae. To reduce light exposure without harming the tank’s inhabitants, make sure your tank is out of direct sunlight and is exposed to artificial light for no more than 8-10 hours a day.
  • Change your water. Nitrate and phosphate build up in tank water over time, even if you take impeccable care of your tank. To ensure this doesn’t cause algal growth, change some water from your tank periodically – ideally, you should change about 10-25% of the water in your tank per week.
  • Feed your fish less. Fish owners tend to overfeed their pets, and – as mentioned above – algal growth is driven by an imbalance in light and nutrients, the latter of which partially comes from fish food. Control feed portions and remove any uneaten food from the tank.
  • Consider adding algae-eaters. As mentioned above, some fish enjoy eating algae. Adding these fish to your tank means that even if there is an increase in algal growth, your fish will take care of it before it becomes a significant issue.

Final Thoughts

Algae cause significant swings in the pH levels of the water in your aquarium and prevent light from reaching your plants. They will stunt the growth of aquarium plants and, uncontrolled, can kill your fish.


Written by:

Pet Aquariums

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