Aquatic plants turning yellow is usually a sign that certain factors required for their survival are compromised. This causes plant stress, resulting in discoloration.
The most common causes of yellowing in aquatic plants are transplanted stress, lack of light, aging, water quality, and nutrient deficiency.
In this article, we will discuss the different reasons your aquatic plants may be turning yellow and how to remedy each one.
Why are my aquatic plants turning yellow?
Transplant stress
Like all plants, aquatic plants also need time to acclimatize to their new surroundings. It requires a delicate balance to accurately simulate an aquatic plant’s natural habitat, so it should come as no surprise that these plants react as they do when placed in a new aquarium.
Try to create conditions as close as possible to the plants’ ideal habitat, and they should recover in no time.
Lack of light
Aquatic plants, just like terrestrial plants, need plenty of light to conduct photosynthesis properly. Yellowing could be due to insufficient time under the light, or a light source that does not have the right intensity for the plant. If a plant is unable to perform photosynthesis, it will not be able to make its own food, so it will not grow healthily and will eventually die. Thus, aquatic plants should be provided with around six to eight hours of light daily, be it natural sunlight or with the help of a grow light.
Aging
Another reason your aquatic plants may be turning yellow is if they are getting old. Older aquatic plants will eventually lose their ability to absorb the nutrients they need to survive, and thus turn yellow. The longer they go on without these nutrients, the faster they will rot and die. If you have any aging plants in your aquarium, remove them completely or cut off the yellow leaves. These rotting plants may change the quality of the water in your aquarium if left there for longer than necessary.
Water quality
Another reason aquatic plants turn yellow is water quality and the environment in the aquarium. You should do extensive research regarding the plants you own and any plants you plan to add in the future. Know the pH, water temperature and any other requirements they might need in order to thrive. This way you can mix and match aquatic plant species that live well together in roughly the same type of environment.
Nutrient deficiency
Aquatic plants can also turn yellow due to a lack of one or several nutrients. Like all other forms of life, these plants also need the right balance of nutrients to be healthy and live a long life. Yellowing is only one of the many problems that can result from a lack of nutrients.
You can tell that your plant has a nutrient deficiency by observing its leaves closely. It can be tricky to tell the symptoms of nutrient deficiency apart, because many of them resemble one another, especially in the eyes of a new plant owner. Pay close attention to the color of the plant’s leaves to make it easier to figure out what it needs.
Here are some things to watch out for when trying to establish which nutrient your plant is missing:
- Older leaves turning yellow with green veins is a sign of iron deficiency.
- Older leaves turning yellow and dying is a sign of nitrogen deficiency that is just starting.
- Aquatic plant leaves with yellowing edges and holes in them are indicative of potassium deficiency.
- Older leaves that are lighter in color with dark-colored veins may mean your plant has a magnesium deficiency.
- New leaves or growth that becomes pale and twisted could mean a calcium deficiency.
- Older leaves turning yellow with dead patches is probably due to a phosphate deficiency.
- Leaves that grow smaller than normal and turn yellow probably indicate a serious and urgent nitrogen deficiency.
How do you help your aquatic plants recover from a nutrient deficiency and keep them from turning yellow?
If the cause of the yellowing is a nutrient deficiency, you need to make sure that they receive the deficient nutrient by making it readily available in their water.
There are also other factors to consider to keep your aquatic plants happy:
Carbon dioxide
Plants need carbon dioxide in order to grow. Some people use supplemental carbon dioxide to help improve their aquatic plants’ growth rate, size and color. You can also do this by using carbon supplements in tablet or liquid form.
Water quality
Each plant has different requirements when it comes to their water, but most aquatic plants need a pH between 6.5 and 7.
Aquatic plants like their water temperature between 75 and 80 degrees Fahrenheit. The water in the tank also needs to be changed 10% if you do it every week, and 25% if you change it fortnightly.
Proper circulation is important to aquatic plant health. It helps prevent the growth of algae and keeps organic waste from accumulating on the leaves.
Light
The type of plants you want and the height of your tank will help determine the amount of light your aquatic plants will need. There are species that need more light than others. You should take these into consideration, especially since water can make it difficult for light to reach the plants. If you feel that the sunlight that reaches your aquarium is too weak, you may have to install a grow light, especially for a tank that is taller than normal.
Aquatic plants prefer full-spectrum light, so choose a light designed for plants, such as an LED.
Aquatic plants need six to eight hours of uninterrupted light daily in order to grow properly. Remember that keeping a weak light on for longer than eight hours is not going to make up for what a sufficient light is able to provide. Make sure you follow a night and day pattern as the plants would experience in nature. Nowadays, grow lights can be hooked up to a digital timer so that you do not have to remember when to turn the lights off and on.
Lastly, always check the glass covers on your tank to make sure they are clean, so that the light can pass through strongly and consistently.
Substrate
Aquatic plants like to be planted in coarse sand or fine-to-medium gravel, but it is always best to do your research and know what kind of medium your plants need. You can mix and match the different grades to get the textures that your plants require.
Try to avoid using sand that is too fine because it can be too compact and affect the breathability of the medium. Gravel that is too coarse, on the other hand, can be loose and unable to anchor the plant properly.
Try not to use carbonate-based substrates such as crushed oyster or dolomite, because they can increase the tank water’s alkalinity and be unsafe for the plants and animals in the tank.
Nutrients
Aquatic plants need nutrients and minerals such as iron, magnesium, potassium, calcium, phosphorus and nitrogen. Phosphorus and nitrogen can be provided by the fish waste and uneaten fish food, but this might not be enough and you may need to add these minerals regularly.
Aquatic plants absorb nutrients through their leaves and roots. You can mix in an iron-rich clay, like laterite, to help the roots absorb nutrients more effectively.
You can provide these important nutrients with tablets specifically formulated for aquatic plants. Tablets meant for houseplants may not benefit your aquatic plants as much.
Conclusion
Yellowing aquatic plants is a sign of stress due to an environmental factor. You need to identify the factor that is causing this change in color before your plants become more damaged.
The most common causes of yellowing aquatic plants are transplant stress, lack of light, aging, water quality and nutrient deficiency.
Aquatic plants are very different from houseplants in terms of their requirements for growth. Make sure you do plenty of research and try to simulate their natural habitat as best you can in your tank.
Image: istockphoto.com / TT