7 Reasons Your Aquarium Plants Are Turning Yellow (& What To Do)

The last time you checked, your aquarium plants were a tropical green jungle in your fish tank. Now, they are starting to turn yellow and die.

Instead of throwing your plants out and starting over, here are 7 reasons your aquarium plants are turning yellow!

Key Takeaways:

  • Aquarium plants turning yellow can be due to several factors, including water temperature, disease, lack of fertilizer, lack of light, and nutrient deficiencies.
  • Proper water temperature maintenance, addressing diseases promptly, providing the necessary nutrients through fertilizers, ensuring adequate lighting, and monitoring and adjusting pH levels can help prevent yellowing.
  • Nutrient deficiencies such as iron, nitrogen, phosphorus, potassium, magnesium, and calcium can cause yellowing and need specific remedies.
  • In some cases, older plants or old leaves may naturally turn yellow, and replacement mightbe necessary.
  • Proper plant selection, tank arrangement, and maintenance practices are crucial for preventing yellowing of aquarium plants.
  • Identifying and addressing nutrient deficiencies in plants involves observation, water parameter checks, and experimentation with nutrient supplements.
  • Removing yellowing plants is not always necessary, and they may recover with proper care and maintenance.

Why Are My Aquarium Plants Turning Yellow?

If you’re wondering why your aquarium plants are turning yellow, then here are the 7 most common reasons!

1. Water Temperature

If your aquarium plants are turning yellow, the water in the tank might be too cold. Since green leaves will turn yellow if the water stays cold for a long time as the plant’s growth will slow, so it’s a good idea to check the temperature of your tank.

While the temperature required for each plant may vary, generally, it’s best to keep the water at 74° to 80° F to avoid plants turning yellow.

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2. Disease

If you typically keep your aquarium at optimal temperatures, it’s time to check to see if a disease is causing your plants to turn a yellow color. Yellowing leaves are often an initial sign that disease is present in the tank. Fortunately, if you act quickly you can often remedy the situation!

3. Lack of Fertilizer

A third reason that your plants can turn yellow is a nutritional deficiency. If your plants aren’t getting the fertilizer that they need, they won’t have the ability to grow and fight off disease. If your plants keep turning yellow, there’s a good chance that they need fertilizer. These can include a liquid fertilizer, base fertilizer, or root fertilizer, depending on the type of plant.  #

4. Lack of Light 

Like most plants, aquarium plants need enough light to keep them from dying. Although they might live among rocks and fish at the bottom of a tank, aquatic plants require a minimum of 10-12 hours of light to thrive.

If your tank doesn’t have access to a sufficient sunlight source, you will need to install a full-spectrum fluorescent light or LED REB light to help your plants flourish. Make sure that they receive at least 6-8 hours of sunlight or strong artificial light for a chunk of time every day.

5. Nitrogen, Potassium, Iron, or Magnesium Deficiency

If your aquatic plants are turning yellow, it’s time to get scientific with their nutrient list. If a plant doesn’t receive specific nutrients such as potassium, magnesium, iron, or nitrogen, it can’t create chlorophyll which keeps leaves green.

Check your plants’ foliage. If a potassium deficiency is causing the leaves to turn yellow, the yellow tinge will occur towards the edge or tip of the leaves. Magnesium deficiency can also be a culprit if the leaves turn yellow while the veins on the leaf stay green.

Aquatic plants need and intake nitrogen in several ways that include ammonia, nitrate, and urea.

You can identify a lack of nitrogen by checking the older leaves on the bottom. If they turned a translucent yellow, then it’s time to add some nitrogen to your water column. The final nutritional reason that can cause plants to yellow is an iron deficiency. With a lack of iron, the leaves will fade out to a pale-yellow hue.

6. pH Levels

Another reason that can cause aquatic plants to turn yellow is if there are the wrong pH levels in the tank’s water.

For example, most aquariums require a pH that lies between 6.0 and 8.0. Keep nitrates below 10 ppm, while phosphates need to fall below 0.5 ppm to prevent algae growth and yellowed leaves.

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7. Old Plants

If you’ve tried everything on this list and your plants don’t respond to treatment or turn yellow again, it’s possible that your plants are turning yellow due to the aging process.

Since older plants can’t keep consuming nutrition, they will eventually degrade and die. If that’s the case, you won’t be able to change or stop this process and will just need to replace your plants when they die.

8. The Leaves Are Old

Sometimes, it’s not the plant that’s getting old but the leaves themselves. If you notice that some leaves are turning yellow, however, there are new leaves growing, then it could just be part of your plants natural life cycle! This is especially true for plants that you’ve just bought! The following is a great explanation:

plant emersed vs submersed leaves

How to Avoid Aquarium Plants Turning Yellow

1.    Choose the Right Plants

To keep your plants from turning yellow, it’s important to choose the proper plants in the first place. Take time to research the kinds of plants that will flourish in your aquarium. You can even reach out to an aquatic plant expert for more advice.

For example, if you want to have some tall plants or species that grow faster, put these at the back of your tank. Put shorter plants in front so that they aren’t blocked by bigger plants.

If you have broadleaf plants, arrange these in the center of the tank. If you have foreground types, they can expand sideways, so it’s best to make sure that your tank is big enough to allow for lateral growth.

Finally, don’t put short plants right next to broadleaf plants. These species create taller foliage that can prevent light from getting all the way to the back of the tank.

Careful selection and arrangement can help you maximize your light source and avoid yellow plants that are overcrowded or don’t receive enough light.

2.    Check pH and Clean the Tank

As discussed, you will want to check the pH levels and maintain a clean tank by cleaning it every two weeks. You will also need to change the water often. This means that you will want to change up to 25% of the water twice a week.

Use bio media for a filter since this reduces organic waste that causes cloudy water and prevents light from penetrating into the tank. Try reverse osmosis or deionized water to keep your plants green and healthy.

3.    Fertilize

Ensure that your aquatic plants have the nutrients that they need by adding fertilizer that is rich in nitrogen, potassium, phosphorous, iron, and magnesium minerals.

If you have the kind of plants that consume nutrients via their root system, you can add a kind of clay-rich iron called laterite or another type of substrate. Make sure that you get a formula that is specifically created for aquatic plants rather than houseplants.

Although fish and food bits do add some nitrogen and phosphorous, you’ll want to regularly pour these micro-minerals into the water to keep your plants happy.

4.    Don’t Fertilize Too Much

Moderation is key here. Although fertilizers can help your plants grow and keep them green, too much of a good thing can turn toxic.

If you add too many nutrients to an aquarium too fast, it can create a chemical reaction that scorches the foliage and turns leaves yellow.

5.    The Carbon Factor

This one’s easy to miss when you’re looking for ways to keep your plants from turning yellow. Carbon is a vital part of growing healthy aquarium plants. These underwater plants absorb CO2 during the day, then reverse that process at night. Some plant experts add extra CO2 during the day to help plants grow faster and maintain their foliage color.

You can add carbon to the tank with a tablet or liquid supplements. Another option is to make your own yeast generator at home. One of the best ways to add carbon to your plants’ diet is to install an injection system that works with pressure and tank lighting to boost growth and health results.

6.    Let There Be Light

Keep in mind that your aquarium plants will vary depending on the type of plants used and the size of your tank. If you have a taller tank that is filled with plants, make sure that the light source that you install is stronger.

In general, aquatic plants need full-spectrum light. The color temperature should be from 6,500K – 8,000K. You can use a plant-specific light source such as an LED or T5 fluorescent with a high output. Using a timer can help keep a consistent and natural pattern that mimics daytime and nighttime.  

7.    Be Consistent

As with everything, consistency is essential. If you add fertilizer every day, keep doing it. Don’t add nutrients one day, and then forget about it the next day. Inconsistency can confuse aquatic plants and make them consume nutrients from their own system rather than depend on an erratic feeding schedule.

Keep lights running on a schedule. Make any changes slowly and keep it consistent. Over time, your plants will adapt and thrive in a consistently healthy environment. It may take some time for damaged or yellow leaves to regain their color. Experiment, and hopefully, your plants will soon return to normal.

1. Water TemperatureMaintain the tank water temperature between 74° to 80°F to prevent plants from turning yellow.
2. DiseaseCheck for diseases if optimal temperatures are maintained. Act quickly to remedy the situation.
3. Lack of FertilizerProvide the necessary nutrients through liquid, base, or root fertilizers, depending on the plant type.
4. Lack of LightInstall full-spectrum fluorescent or LED lights for 10-12 hours a day to ensure plant growth.
5. Nutrient DeficienciesIdentify specific nutrient deficiencies (potassium, magnesium, iron, nitrogen) and address them accordingly.
6. pH LevelsMaintain the pH between 6.0 and 8.0 and control nitrates and phosphates to prevent yellowed leaves.
7. Old PlantsAccept that older plants may naturally turn yellow and consider replacing them when necessary.

How To Raise Nitrogen For Aquarium Plants?

Adding nitrogen to aquarium plants is an essential aspect of keeping them healthy and thriving. Nitrogen is a vital nutrient for plants and plays a significant role in their growth and development. Let’s go over some steps on how to add nitrogen to your aquarium plants.

  1. Understand the Nitrogen Cycle

Before considering adding nitrogen to your aquarium, it is essential to understand the nitrogen cycle. This cycle is the process by which beneficial bacteria break down waste products in the aquarium, converting ammonia to nitrites and then to nitrates.

Nitrates are then utilized by plants as a source of nitrogen. Therefore, maintaining the nitrogen cycle in your aquarium is crucial to ensure your plants have a steady supply of nitrogen.

  1. Use Fertilizer

Fertilizers are a quick and easy way to add nitrogen to your aquarium plants. There are two types of fertilizers: liquid and substrate fertilizers. Liquid fertilizers are added directly to the aquarium water and are quickly absorbed by the plants. Substrate fertilizers are buried in the aquarium substrate and slowly release nutrients into the water.

  1. Consider Fish Waste

Fish waste is another source of nitrogen for aquarium plants. If you have fish in your aquarium, their waste products will break down into ammonia, which can then be converted to nitrites and nitrates through the nitrogen cycle. However, it is essential to monitor the levels of ammonia and nitrite to ensure they don’t become toxic to your fish.

  1. Utilize CO2 Injection

Carbon dioxide (CO2) injection is another way to increase plant growth by enhancing photosynthesis. CO2 is essential for plants to produce carbohydrates, which are used for growth and energy. Adding CO2 to your aquarium can help your plants absorb more nitrogen and other nutrients.

  1. Maintain Lighting

Light is an essential component of photosynthesis. Therefore, providing adequate lighting for your aquarium plants is crucial to ensure they can absorb nutrients and grow effectively. LED lights are a popular choice for aquariums as they provide a natural-looking light that promotes plant growth.

And remember when it comes to most aquarium plants, you should aim for 3-5 watts per gallon.

3-5 watts of lighting per gallon

What Nutrient Deficiencies Can Aquarium Plants Get?

Aquarium plants require specific nutrients to grow and thrive. Nutrient deficiencies can have adverse effects on their growth and appearance. Here are the most common nutrient deficiencies that aquarium plants can experience:

  1. Iron Deficiency

Iron is an essential nutrient for aquarium plants as it plays a crucial role in chlorophyll production. Chlorophyll is the pigment responsible for the green color in plants, and its absence can lead to yellowing, or leaves that are light green with dark veins. Iron deficiency can also cause slow growth, stunted plants, and weak stems.

  1. Nitrogen Deficiency

Nitrogen is another crucial nutrient required by aquarium plants. It is essential for the production of amino acids, which are the building blocks of proteins. Nitrogen deficiency can cause the leaves of the plants to turn yellow all over, stunted growth, and small leaves.

  1. Phosphorus Deficiency

Phosphorus is an essential nutrient that is necessary for photosynthesis and energy production in aquarium plants. Phosphorus deficiency can lead to stunted growth, dark green leaves, and weak stems.

  1. Potassium Deficiency

Potassium is essential for many plant functions, including the regulation of water balance and enzyme activation. Potassium deficiency can cause yellowing of the edges of leaves, stunted growth, and small leaves.

  1. Magnesium Deficiency

Magnesium is necessary for the formation of chlorophyll, and its deficiency can cause yellowing of leaves, slow growth, and weak stems.

  1. Calcium Deficiency

Calcium is required for the formation of cell walls in plants, and its deficiency can cause stunted growth, distorted leaves, and weak stems.

Check out this video on the most common reasons for yellow leaves as well as the cure:

How To Identify Nutrient Deficiencies In Your Tank?

Identifying nutrient deficiencies in your aquarium plants is crucial to maintain their health and growth. So, let’s discuss the steps to help you identify nutrient deficiencies in your tank:

  1. Observe the Plant

The first step to identifying nutrient deficiencies in your aquarium plants is to observe them closely. Look for any signs of discoloration, wilting, or stunted growth. Check the leaves for any yellowing or browning, as well as the overall size and shape of the plant.

  1. Check the Water Parameters

Check the water parameters in your aquarium, including pH, hardness, and nutrient levels. You can use a water testing kit to measure the levels of nitrate, phosphate, and iron, among other nutrients.

  1. Compare Symptoms to Nutrient Deficiencies

Compare the symptoms observed in the plant to the common nutrient deficiencies. For example, yellowing of the leaves may indicate a nitrogen deficiency, while brown spots on the leaves may indicate an iron deficiency.

  1. Experiment with Nutrient Supplements

To confirm a nutrient deficiency, experiment with adding the missing nutrient to the aquarium. You can add fertilizers or supplements specifically designed for the missing nutrient and observe the plant’s response. If the plant’s condition improves, it confirms that it was a nutrient deficiency.

  1. Seek Professional Advice

If you are unsure about the nutrient deficiency or need further assistance, seek professional advice. You can consult with a knowledgeable aquarium store employee or a professional aquarist to help you identify and treat the deficiency.

Aquarium plants turning yellow

How To Fix Nutrient Deficiencies In Plants?

Once you have identified the nutrient deficiency in your aquarium plants, it is essential to take corrective measures to fix the problem. Here are the steps to fix nutrient deficiencies in your plants:

  1. Determine the Missing Nutrient

Identify the nutrient that is missing from the aquarium. Use the symptoms observed in the plant and water testing results to determine which nutrient is deficient.

  1. Add Nutrient Supplements

Add nutrient supplements specifically designed to treat the identified nutrient deficiency. You can add fertilizers or supplements that contain the missing nutrient in the appropriate amounts.

  1. Adjust Water Parameters

Adjust the water parameters in your aquarium to optimize nutrient uptake by the plants. For example, if you have identified an iron deficiency, adjust the pH level to make it more acidic, which helps increase iron availability.

  1. Reduce Light Intensity

If your plants are experiencing nutrient deficiencies due to excessive light, reduce the light intensity by adjusting the lighting schedule or using shade cloth or other light-blocking methods.

  1. Prune Damaged Leaves

If the nutrient deficiency has caused damage to the plant, prune the damaged leaves to allow the plant to redirect its energy towards new growth.

  1. Maintain Regular Water Changes

Maintain regular water changes to remove excess nutrients and prevent nutrient buildup in the aquarium. This helps prevent nutrient imbalances and deficiencies from occurring.

  1. Monitor Plant Health

Continue to monitor the health of your plants and adjust nutrient supplements and water parameters as needed. Regularly observing your plants helps identify any further nutrient deficiencies and take corrective measures promptly.

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Here are some other frequently asked questions that people have about their plants turning yellow, as well as other nutrient deficiencies!

What Is The Ideal Ph And Temperature For The Aquatic Plant When They Start To Turn Yellow?

The ideal pH and temperature for aquatic plants can vary depending on the species, but in general, a pH range of 6.0-8.0 and a temperature range of 72-82°F (22-28°C) are suitable for most aquarium plants.

Should You Get Rid Of Aquarium Plants That Are Turning Yellow?

Not necessarily. While yellowing of aquarium plants can indicate a problem, it doesn’t always mean that the plant is dead or beyond saving. However, if the plant is severely damaged or infected, removing it may be necessary to prevent the spread of disease or further damage to other plants.


If your aquatic plants are turning yellow, it’s usually an easy fix with some time and effort. It may take a little detective work to determine if your tank pH is off or if your plants need some nutritional support.

Like most living things, marine plants need light to survive, so flip the switch, open the curtains, or move the tank to a location where your plants can receive light. Maintaining a clean tank will not only make your aquatic world sparkle, but it will reduce bacterial diseases that can cause plants to turn yellow.

The good news is that it is entirely possible to stop your aquatic plants from turning yellow and create a healthy underwater place for your fish to thrive.

About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!