Why Are My Aquarium Plants Turning Brown?

There are a lot of benefits to keeping live plants in your aquarium. Not only do they create a more natural-looking environment for your fish, but they also improve water quality by using up excess nutrients and oxygenating the water.

Live plants definitely add another level of beauty to any tank setup, but it’s not always easy to care for them. One common problem is aquarium plants turning brown. When this happens, they’re no longer nice to look at and may cause harm to your fish by affecting the chemistry of the water.

Let’s take a look at some of the common reasons aquarium plants turn brown, and what you can do to treat it or prevent it from happening in the first place.

Nutrient Deficiencies

Plants need a variety of nutrients to grow. If something is missing, your plants will suffer.

Remember that all nutrients and trace elements are independent of one another. Just because there’s enough of one doesn’t mean there’s enough of everything. When testing the water, check for a range of nutrients to be sure everything is covered.

The most important nutrients for aquarium plants are:

Magnesium

Magnesium is one of the key nutrients that contributes to the green pigment of aquarium plants, and a deficiency is likely to cause discoloration in older, established plants. One notable sign of a magnesium deficiency is that the leaves themselves turn yellow or brown while the veins remain green.

Micronutrients

Your plants only need micronutrients in small amounts, but they are necessary for plants to grow green and healthy. Examples of micronutrients include boron, calcium, zinc, and manganese.

The most important micronutrient for plant growth is iron. An iron deficiency causes less chlorophyll to develop, causing leaves to stay light green. If the deficiency is serious, the leaf tips are lighter and, eventually, begin to turn brown and black. New plants are more likely to be affected by an iron deficiency.

Nitrogen

If you have an established tank and notice the plants are starting to turn brown at the tips, check the nitrogen level. You may also notice stunted growth or lack of new growth, and the leaves can begin to take on a reddish color.

Phosphorus

Phosphorus is present in your aquarium water as phosphate, which is what most water-testing kits measure. Your plants need just the right amount of phosphate to thrive. If the phosphate is low, plants grow poorly and have small shoots.

On the other hand, too much phosphate leads to brown spots. It can also cause excessive algae growth, which leads to a lot of other issues in your tank. As you can see, monitoring the phosphate level is essential to keeping a planted tank healthy.

Potassium

Another thing that can cause aquarium plant leaves to turn brown is a lack of potassium. This commonly starts as black dots. Eventually, these dots progress to holes, and the rest of the leaf turn brown or yellow.

Carbon dioxide can also affect potassium levels. Strong aquarium lighting can stimulate plants to release more carbon dioxide, and some fertilizers may elevate the levels, too.

Carbon Dioxide

We hinted at the importance of carbon dioxide, but having the right amount is essential for healthy plant growth. Plants need carbon dioxide for photosynthesis, which gives them the energy they need to grow.

Most aquariums don’t require added carbon dioxide, but if you have a tank with only a few fish or one that is heavily planted, it can be an issue. If your plants aren’t growing well or if you notice discoloration, you may need to add some carbon dioxide.

Substrate

Think about substrate like you do the soil in your garden – it’s one of the most important factors to supporting healthy plant growth. Substrate gives the roots the nutrients they need to grow. If the substrate is compacted and the roots have a hard time pushing through or if the nutrients are all used up, your plants might start turning brown due to the previously mentioned deficiencies.

Other Reasons Your Aquarium Plants Are Turning Brown

Here are some other reasons the plants in your aquarium may be turning brown:

Brown Algae

Brown algae are not actually algae at all, but small organisms called diatoms. If your plants, the sides of the tank, decorations, and everything else in your tank is getting covered in the brown film, diatoms are likely the cause.

Diatoms are difficult to get rid of, but there are a few things you can do. First, clean your tank really well to get rid of as many as you can. Remove everything you can from the tank and scrub it clean. Then, check the water chemistry. Diatoms like nitrates and keep coming back as long as they have something to eat.

Adding movement to your water can help prevent diatoms, too. These tiny creatures are not strong enough to hold onto your plants or decorations when there’s a current.

Make sure your tank isn’t exposed to too much light and remove anything with silica from your tank. Diatoms eat silicates, too, so remove rocks or sand that contain silica from the tank.

New Plants

Another thing that can contribute to your plant turning brown is its age. In some situations, new plants turn brown while adjusting to the new environment, but once you understand how these plants are grown, it makes sense why this happens.

Most aquarium plants are grown above water. Large pet stores often sell them this way, with each plant’s roots covered in moist gel and the leaves enclosed in a plastic tube. In this case, the leaves are accustomed to living in the air.

When you add these plants to your tank and submerge them in water, they may take a while to adjust. In some cases, the leaves will turn brown and eventually fall off while new water leaves grow.

Animals

Some of the creatures you keep in your aquarium may be chowing down on your plants. When these animals damage the integrity of the leaves, they turn brown and, if the damage is severe enough, the plant may die.

Light

We mentioned that too much light causes leaves to turn brown, but not enough light causes damage, too. Just like houseplants, aquarium plants each have different light requirements. Research plants before adding them to your tank to make sure you give them the light they need.

How to Care for Aquarium Plants?

To make sure your plants stay healthy, do regular checks on the overall health of your aquarium. If you have fish or other creatures in your tank, you should already be performing regular water changes and checks. Include your plant life in your regular maintenance.

A planted tank needs a good, nutrient-rich substrate to thrive. Test the water regularly to make sure there are enough nutrients, and keep the tank clean. Research your plants before adding them to the tank to make sure you’re giving them the right amount of light.

When planning your tank, spend some time researching your fish, too. Create an environment that’s as natural as possible by choosing plants and fish that coexist in the same environment in the wild.

This is beneficial for a lot of reasons, but one of the main ones is that the plants and fish will be happy in the same water conditions. Overall, this makes it much easier for you to take care of your tank.

Troubleshooting

If you notice the plants in your aquarium are starting to turn brown, take action quickly. Any problem you have is only going to get worse if you wait. If you have a new setup, expect a little bit of adjustment time, but pay close attention to catch any problems when they start.

If you have an established tank that was doing well, but suddenly your plants are turning brown, do a water test. This lets you know if you have a nutrient deficiency so you can correct the problem.

Remember, the easiest way to stay on top of things is to perform regular maintenance on your aquarium. Check the water regularly, and keep a close eye out for any changes.