Aquarium plants require constant attention to grow right. Unfortunately, it is pretty common for them to lose their natural color, despite all you do to maintain them.

The primary reason aquarium plants turn black is the growth of black algae. However, inadequate light, water, and nutrients could also play a role.

To prevent or stop this occurrence, it’s essential to familiarize yourself with all these causes and how to tackle them.

plants-turning-blackWhy Your Aquarium Plants Are Turning Black?

The overall health of your aquarium plants depends on several factors, including:

The types of plants grown
Light levels
The size of the tank
Other living organisms in the tank

The first sign that something is wrong with one or more of these factors is plant discoloration. When your plans turn black, diagnose the following factors:

1. Nutrients

Nutrient deficiency is a fairly common problem for plants regardless of their environment.

A plant needs to consume various nutrients to maintain optimum health and functioning. However, nitrogen, phosphorus, and potassium are the most important.

dying-plantThere are several signs to tell which nutrient your plant is missing or having an abundance of. These signs include:

Nitrates: Excess nitrates may damage the plant, causing it to turn brown or black before dying. Nitrate concentrations are high in tanks that haven’t been cycled completely.
As a result, they lack sufficient beneficial bacteria to digest the waste products produced by aquarium organisms.
Iron: In an iron-deficient tank, new leaves will become yellow. The veins in mature leaves turn green and become translucent.
However, this is only true when iron deficiency is in its early stages. Before the plant withers, the leaves will become black in advanced cases.
Phosphates: If there isn’t enough phosphate in the tank, the leaves will turn yellow and disintegrate. On the other hand, excess phosphate causes the leaves to turn black.

How To Solve This?

Use the guide below to augment scarce nutrients or reduce the excessive ones. Be careful on the adding part, as too many nutrients can aggravate underlying problems and cause algal blooms.

Excess Nitrates: To reduce excess nitrates in your aquarium, stop overfeeding your fish and other organisms, as it leads to the production of excessive nitrates as waste byproducts.
Ensure that your aquarium isn’t overpopulated and clean it regularly.
Potassium: You can get rid of potassium deficiency by adding some root tabs and liquid fertilizer containing potassium.
Phosphorus: A simple water change can eliminate the excess phosphates in the tank and improve plants’ health. Use alternate sources of water if your tap water has high phosphorus levels.
Iron: Use specific fertilizers rich in iron to remove deficiencies, as general-purpose fertilizers don’t always contain enough of it.

2. Water Quality And General Tank Hygiene

leaves-darkeningWhen it comes to your aquarium, water quality relates to factors such as pH, ammonia, dissolved oxygen, and salts. These factors determine the overall health of your aquatic plants and animals.

If there is too much ammonia in the water, your plants will usually start to change color and wither.

Furthermore, the water in an aquarium should be as neutral as possible. Plant health can be harmed by pH levels too high or too low.

Similarly, an unhealthy and dirty tank would only promote germs and bacteria and impede the plant’s growth.

How To Solve This?

Water quality problems can be due to a wide range of reasons. However, they majorly revolve around ammonia and pH.

Closely monitor the quality of the water and maintain excellent tank hygiene:

Clean out your tank regularly, change the water often and keep your tank free from harmful chemicals.
●Use Deionized (DI) water or Reverse Osmosis (RO) water if the tap water quality isn’t acceptable. Be mindful that you may need to add additional minerals.
Avoid crowding your tank with plants. This allows for sufficient space and enough nutrients.
Check each plant’s requirements before moving them to the tank.
Wash your hands before and after handling the plants and cleaning the tank.
If your tank has a filter, clean out the filter every time you clean out the tank.

3. Algae

algae-in-aquariumAlgae can also negatively affect aquarium plants. One such type of algae is the Black Beard Algae.

A dirty tank or overexposure to light promotes the growth of these algae. Excessive use of fertilizers or nutrients such as iron and phosphate or the lack of them also contributes to their multiplication rate.

Black Beard Algae grow in different color shades, including dark green, black and gray. They tend to grow quickly and outcompete the aquarium plants for light and nutrients.


Regular water changes can help in getting rid of the black algae. Clean out the tank and get rid of dirt and waste.
Another way to get rid of this algae is by starving it. To do this, add some phosphate-eradicating resin.
● You can also consider a natural eradication method by adding some Amano shrimps. These shrimps feed on algae.
Keep your tank away from the window. Too much sunlight can make them multiply fast and block sunlight for aquatic plants.

It is important to note that regardless of which method you choose, you would need to do it for at least a month to get positive results.

4. Improper Lighting

blackening-leavesImproper illumination is another typical cause of plant leaves turning black.

Over-lighting is a common mistake made by new aquarium owners. It promotes the growth of algae which in turn starve the plants for light, making them turn black.

Tank owners also sometimes tend to keep their aquariums reasonably dark. They usually do it because some deep water fish and other organisms might not be suited to bright light.

Again plants will turn black if they don’t get enough light.


Always make sure your tank is adequately illuminated according to the plant and animal species thriving in it.

Whether using natural sunlight or artificial lighting, you should not expose your aquatic plants to more than 12 hours of light per day.

In the same way, they should not spend more than 12 hours in the dark.

5. Improper Planting

yellow-leavesAs a plant owner, you should always conduct enough research about each plant before introducing them to the aquatic tank.

Each plant species has its own set of needs and space requirements. An overcrowded aquarium is as bad as one with incompatible plant species.


Make sure each plant’s roots are correctly positioned and adequately spaced. Some plants might have an extensive root system requiring ample vertical and horizontal space to expand.

● Ensure that all plants are compatible and grow well under similar conditions and with similar nutrients.

Ensure that your substrate is properly settled and distributed in the tank and that it isn’t clumped together.

Essential Tools And Equipment

You must have the below-mentioned tools and equipment for problem diagnosis and general maintenance of your aquarium.

1. pH Test Kits

This will help you monitor your aquarium pH levels. Excessively high or low pH levels are usually the first indicators that tell if something is wrong with your aquarium.

2. Digital Aquarium Thermometer

Some undesired chemical processes in your aquarium can alter its temperature. A well-calibrated and accurate digital thermometer can help detect these temperature changes.

3. Aquascaping Tools

These tools make planting and replanting your aquatic plants easy and straightforward. They also help you clean and maintain your aquatic tank for healthy plant growth.

4. A Gravel Vacuum

A gravel vacuum is as vital to an aquarium enthusiast as a shovel is to a gardener. It helps in effectively cleaning the aquarium substrate of dirt, debris, food leftovers, and byproducts such as fish poop.

5. Liquid Plant Fertilizer

A liquid plant fertilizer can help in effectively helping your plants grow. Make sure that it is well balanced in all the essential nutrients.


The leaves of your aquatic plants could be turning black due to various reasons. These range from algal blooms to lack of nutrients and bad lighting.

Luckily they can be resolved relatively quickly with timely diagnosis and proper care. Our handy troubleshooting guide above has all you need to restore normalcy to your aquarium.

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