I am a fan of planted aquariums and started my first planted tank back in 2013. They can bring the visual appeal of your aquarium to a level that no other item can do.
I must admit keeping live plants is relatively more challenging than just keeping fish from my own experience. But I never gave up. I was in love with the greenery, and I learned how to maintain them. Although resources were limited, experience, study, and research finally delivered me the desired outcome.
I often receive a common question on different platforms; why are my aquarium plants turning brown? Aquarium plants are sensitive to water conditions. If the tank water condition deteriorates, plants show the first warning sign that things started going wrong!
Plants are beneficial for keeping balance in the aquarium. They absorb CO2 and other toxic matter and, in return, add oxygen to the water. But plants themselves need a balanced combination of light, CO2, and other nutrients. In this article, I’ll discuss in detail why aquarium plants become sick and turn brown.
The primary reason for aquarium plants turning brown
When plants start turning brown, it’s an indication of their sickness and nutrition deficiency. Plants need light and CO2 for the photosynthesis process, which is crucial for their growth and survival.
Photosynthesis is a photochemical reaction that takes place in a plant’s green leaves. By this process, from light and CO2, plants produce sugar and oxygen, which become the source of energy for their survival.
Other nutrients such as nitrogen, phosphate, potassium, magnesium, iron, and manganese are also essential for aquarium plants’ healthy living. Plants collect these nutrients from the aquarium water and substrate primarily through their leaves and roots.
A balanced supply of all the above elements is the key to having healthy plants. Any irregularity (deficiency or surplus) can cause plants to turn pale and brown. I’ll discuss it all one by one.
1) Inadequate lighting
As I said before, lighting is one of the basic needs of a plant’s survival. It’s the source of their energy. As we take carbohydrates from food, plants make sugar from photosynthesis. If the light is deficient, plants will definitely suffer from starvation.
Different aquarium plants have different levels of lighting needs. Typically the fast-growing plants require more energy to grow, hence require intense lighting. Slow-growing plants like Anubias, Java Fern, Marimo Ball, etc., require less. But more or less, all aquarium plants need light. And if it is inadequate, they will suffer from vitality and vigor, resulting in turning brown to death.
Insufficient light symptoms:
- Plant growth becomes slow or no growth at all.
- Mature leaves turn yellow or brown.
- The whole plant turns pale, white, or transparent.
Mitigation for insufficient lighting:
Ensure full-spectrum lighting:
Plants get sunlight in the wild, but indoor aquariums are limited to sunlight exposure. Whereas direct sunlight for aquariums is not advisable as it promotes uncontrolled algae growth. A full-spectrum lighting system is the best solution to provide sufficient light for planted tanks.
Use efficient LED lights:
Nowadays, LED aquarium lights are readily available in the market. LED lights are reliable and cheaper. As long as they are providing the necessary spectrum, plants will thrive.
Know your plant’s need:
As I said before, the level of need for each plant is not equal. You have to know the requirement of your plant. But in general, 1.5 watts of LED lighting per gallon are the minimum requirement for planted tanks with low light plants. For high light demanding plants, the condition is 3 watts of light per gallon.
Keep low-light-demanding plants:
Though your option of choosing plants will shrink by this, low-light plants are hardy and more comfortable to keep. If you are a beginner, I’ll suggest keeping low-light plants (like Anubias, Java Fern, Java Moss, Marimo Ball, Dwarf Rotala, etc.)
2) CO2 deficiency
Then it comes to CO2, which is another essential element for the photosynthesis process. So plants will suffer from the same consequence of light deficiency. CO2 naturally is present in the aquarium water to a certain level.
Low-light plants can do well with the naturally occurring CO2 of aquarium water. But if your aquarium is densely packed with lots of demanding plants, CO2 may become limiting, and plants suffer from starvation. They turn brown and pale to death.
CO2 deficiency symptoms:
- Diminutive plant growth.
- Leaves turn brown and yellow.
- Stems become brown leading to plant death.
CO2 deficiency mitigation:
Select low-demanding plants:
The CO2 requirement of the plant is directly related to their light needs. So, if you select low-light plants, they will consume less CO2.
Maintain a day/night cycle:
Plants consume CO2 in the presence of light and produce sugar and oxygen. But in darkness, they reproduce CO2 from oxygen and sugar by respiration.
Keeping lights off at night helps to develop CO2 levels from fish and plant respiration.
Use a CO2 injection system:
By adding CO2 to the tank water, you can increase the CO2 level. You have to install a CO2 system for injecting CO2 into the aquarium eater.
A standard CO2 injection system consists of a CO2 bottle, CO2 regulator, diffuser, bubble counter, needle valve, and a few other optional accessories.
Reduce the water circulation flow:
If the tank water circulation current is too high and forms many bubbles, dissolved CO2 evaporates from the water. So, reducing the turbulence of aquarium water is another way to keep CO2 dissolved in the water.
Risks associated with high CO2 level
High CO2 levels in the aquarium water can be fatal for your fish. So, especially if you are using a CO2 supplementation system, controlling the dosing rate is crucial.
Very high-demanding plants do well at a CO2 level of 30 mg/l. But the safe level for fish is below 35 mg/l of dissolved CO2. Beyond this, fish start showing signs of stress and lethargy. They lose their appetite, become weak, and may die.
3) Other nutrients deficiency
Besides light and CO2, there are some essential nutrients for plants that help them growing and being healthy. Aquarium plants collect these nutrients from the tank water and substrate.
Some of these nutrients are macronutrients, and plants require them plenty. Nitrogen, Phosphate, Potassium, and Magnesium are macronutrients.
Plants need some amount of Iron and Manganese also, and they are micronutrients. They require a balanced amount of macronutrients and micronutrients. Deficiency and surplus of nutrients both can cause problems.
Nitrogen is a vital nutrient for all kinds of plants, including your aquarium greenery. Aquarium plants collect nitrogen in the form of nitrate, nitrite, and ammonia compounds. Thus, they reduce nitrate, nitrite, and ammonia from the aquarium water and make a healthy fish condition.
In a fully cycled tank, ideally, no ammonia and nitrite should be present. So the primary source of nitrogen of aquarium plants is dissolved nitrates in the water.
Symptoms of nitrogen deficiency
- New leaves appear as curly and reddish.
- Mature leaves turn brown.
- Leaves start falling off.
- Slow growth.
Excess nitrate and ammonia
Nitrogen compounds are essential for plant growth, but they are toxic for fish. If ammonia builds up in a tank, it indicates the tank is not fully cycled; or the nitrogen cycle is somehow disturbed.
Nitrate buildup is a common problem in fish tanks, even in planted tanks. If aquarium plants cannot absorb all the produced nitrate, it will rise in level. Water change is the solution for the above cases. Otherwise, it will stress or even kill your fish.
Excess nitrates in the aquarium water can promote algae growth also.
Maintaining a balanced level of nitrates (5-10 mg/l) in planted tanks is the key. If the nitrate level goes down to zero in a cycled tank, it indicates plants are consuming a lot. And they are probably overcrowded.
Phosphate is an essential nutrient for aquarium plants. Phosphate compounds naturally occur in the aquarium water from many sources, like decaying plant matters, fish wastes, and food leftovers.
Prepared fish feed and organic salts also provide phosphate to the tank water. Phosphate deficiency causes several issues for aquarium plants.
Symptoms of phosphate deficiency
- Holes in the leaves.
- Brown spots on the leaves.
- New leaves start turning yellow.
Symptoms of excess phosphate level
- Plant leaves start turning deep brown to black.
- Excess algae start growing in the aquarium water.
How to overcome phosphate issues
If you observe phosphate deficiency symptoms, add phosphate-rich fertilizer and organic salt to the aquarium water.
For excess phosphate issues, perform water changes and a thorough substrate cleaning.
Related read: Best Fertilizer for providing nutrient to plants
Potassium is one of the salient nutrients for plants that naturally occur in aquarium water. Plants consume plenty of potassium to grow and flourish. So, the inadequacy of it stresses them a lot.
Symptoms of potassium deficiency
- Pinhole starts forming on the leaves.
- Edges of the leaves become pale and yellowish.
How to overcome potassium issues
Maintain a good water condition keeping balance in pH, hardness, and CO2 level.
Potassium supplementation is also useful.
Magnesium is a vital nutrient to maintain your greenery. Magnesium and iron are essential for a plant’s bright green coloration. Whereas magnesium deficiency reduces the plant’s iron absorption capacity. So, they are interlinked.
Symptoms of magnesium deficiency
- Leaves start turning brown with brown and yellow spots.
How to overcome magnesium issues
Fertilization and nutrient-rich plant soil can fix this issue.
Iron is an essential nutrient for the vibrant green color of plants. Iron salts can be present in tap water, but all forms of iron compounds are not soluble. Plants can absorb only soluble iron compounds from the tank water. So iron deficiency is a common issue.
Symptoms of iron deficiency
- Plant leaves start losing green color and turning to be pale, yellowish, and colorless.
- New leaves are grown white and pale.
- Leaves and stem tissues turn necrotic leading to death.
How to overcome iron deficiency
Iron is difficult to absorb from the water. So providing a nutrient-rich substrate is the best solution to overcome iron deficiency.
Plants don’t need manganese in too much amount, but they are important. Mainly, it helps plants’ metabolism to utilize other nutrients effectively and grow.
Symptoms of manganese deficiency
- Plants become weaker, and their growth slows down.
- Plant leaves start turning yellow to brown.
- Start forming holes on the leaves.
How to overcome manganese deficiency
Iron-rich substrates and fertilizers contain traces of manganese and can supplement it.
Other reasons for aquarium plants turn brown
Sometimes aquarium plants may turn brown due to algae formation. Brown-colored algae can form a layer on green plants. It happens mostly in partially cycled tanks. So lack of nutrients may not always be the reason for a brownish plant.
Brown algae are not so harmful as nutrient deficiency, and the mitigation is relatively more painless. Perform a regular water change. Hopefully, the problem will be resolved.
Poor water condition
Plants can absorb some impurities from the water, but not all. Significantly undissolved pollutants can affect the water quality badly. Thus, low water quality can be a significant reason for your plants losing green.
If your tap water contains undissolved iron matters, it can turn plant leaves brownish. Similarly, dirt and debris can cause the same.
Effective mechanical filtration is the key to keep the tank water free from undissolved solids. Perform regular water changes, which is very beneficial to ensure the health of both fish and plants.
The substrate is a crucial consideration for a planted tank as most aquarium plants take nutrients from the substrate. A mineral-riched suitable substrate can encourage your plants to prosper.
Mineral-riched soils are my first preference in planted tanks. But I tried growing plants in gravels, and it works for many plants. Whereas a sandy substrate is not suitable for most aquarium plants.
If you choose the wrong substrate for the plants, it can be a possible reason for your plants turning brown to die.
You have heard it ‘as you sow, so shall you reap.’ The way you planted the aquarium plants makes their future foundation for growing healthy.
Each plant species has a unique technique for plantation. You have to ensure the right way to plant aquarium plants. For instance, some plant roots need to be buried deep in the substrate, while others should not go deep. Some aquatic plants don’t have roots, but some grabbing organs like rhizoids. They also need another particular planting method.
If the planting is not proper, plants cannot settle and grow; instead, they turn brown and die.
Other problems associated with aquarium plants
Holes in leaves
The possible reason for forming holes on the leaves of aquarium plants is potassium and phosphate deficiency. Initially, it creates black dots and then grows visible holes.
Slow growth can be the consequence of all sorts of deficiencies. Inadequate light, CO2, and improper nutrition can slow down the expected growth of your aquarium plants.
If you observe brittle leaves of your aquarium plants, probably the pH level of the water is too high. Check the pH, and if the value is below 7.5, then the possible reason could be something else.
Iron and potassium deficiency also can cause brittleness of plant leaves.
Poor water conditions and excess iron contamination in the water can be the culprit for aquarium plant leaves turning black. Water change is the solution to get rid of it.
How do I get rid of brown algae on my aquarium plants?
Higher nitrates and phosphates in the water are the main reasons for brown algae on plants. Frequent water changes can reduce the nitrate and phosphate level of the water. This is the best solution to remove brown algae.
Do Brown algae mean my tank is cycled?
Not necessarily. Brown algae can appear during the cycling process, which is very common. But it can also occur in an established tank. Brown algae is not a common type of algae, but they are a tiny animal, diatom.
Should I remove dead plants from the aquarium?
Yes, you should remove dead plant matters as soon as possible. Rotten plant parts decompose to form ammonia, which is deadly for fish.
Is it hard to keep live plants in an aquarium?
In my opinion, it’s not. Keeping plants in the aquarium is as simple as keeping fish. Just a few more other things need extra focus to have plants in your aquarium. Light and substrate are the primary consideration among them.
Do live plants need soil in a fish tank?
Particular mineral-riched soils are ideal for growing plants in aquariums. Although there are many kinds of plants that do well in any substrate. You can pick the easiest plants that can grow in gravels and sands also.
The three critical factors in maintaining your greenery are the lighting, water condition, and substrate. Be conscientious in keeping those things right, and your planted tank will burgeon. Keep in mind the following points:
- Choose the right plants and arrange sufficient lighting and a suitable substrate for them.
- Regularly perform water tests and water changes.
- Ensure an effective filtration in place and properly functioning.
- If you keep high light plants, use CO2 supplementations, and operate them properly.
- Pick the appropriate type of fertilizer during fertilization. Liquid fertilizer is useful.