Water consists of many minerals, among which nitrates and phosphates become a matter of concern when you are using it for your aquarium. While aquarium plants need these substances to prepare their food, in high concentrations, they become toxic to fish. It is when learning the art of balancing these minerals and various other compounds becomes necessary.
In this article, we will learn how to deal with the two most critical substances in the aquarium – the phosphates and nitrates. Besides, we will learn the importance of these two substances and answer a lot of questions that beginners as well as expert aquarists often ask regarding them.
Phosphates and Nitrates in Aquarium
Aquarium water consists of many chemicals, minerals, and compounds that usually depend upon its source of collection and environment. From dissolved gases such as oxygen and carbon dioxide, inorganic compounds like phosphates, sulphates, bicarbonates and nitrogen compounds, to organic compounds and trace elements, there is abundance of substances in aquarium water.
In this regard, keeping certain substances in limit becomes crucial for proper growth and development of aquarium plants and fish.
Phosphate (PO4)
Phosphorus, a vital element of life, is the major substance present in phosphate. Being a crucial element, it is needed by every organism to perform various physiological processes. In aquarium water, phosphate can come through various sources–among which human activities plays the major role.
Here are some of some of the major sources-
Fish Food– The nutritional composition of many commercial fish foods has phosphate as the major constituent. When you offer such food to the fish, the phosphate makes the entry into the aquarium. From leftover fish food to fish waste products, everything contains phosphate in them. Tanks with large fish populations are often found to have higher concentrations of phosphate.
Tap Water– In many areas, phosphate is used for the water treatment process. If you add such water directly to the tank, the chances of the introduction of phosphate increase, too.
Aquarium substrate– When you decide to have aquatic plants in the tank and add aquarium substrate, fish waste, uneaten food particles, organic matter, etc accumulate, releasing phosphate in the tank.
Other than these major causes, phosphate may also come through withering driftwood and decorations into the water. At the same time, when the dead plant material start decomposing, they release phosphate.
Nitrate (NO3)
Another important element in the aquarium is the nitrate. While phosphate is added to the water actively or produced after decomposition, nitrate is the result of biological processes and comes as a byproduct.
Here are the major sources of nitrate in aquariums-
Fish Waste– The excreta of fish contain ammonia (NH3), which breaks down into nitrate, and this way, it is introduced into the aquarium water. While ammonia is highly toxic to the fish in the tank, nitrite (NO2) and nitrate (NO3) form immediately, which are its less toxic variants. Ammonia converts into nitrite, and nitrite converts into nitrate with the help of bacteria present in the biological filter.
Organic Matter Decomposition– Different matters in the tank such as dead plant materials, leftover food particles, organic debris, etc. decompose over tome, releasing nitrates to the water.
Tap Water– In certain areas, tap water contains good amount of nitrates as a result of water disinfection process and agricultural runoff.
So, phosphates and nitrates are found naturally occurring substances and help in furnishing basic needs of the organisms as well as aquarium plants. They help in different ways for proper growth and development of the plants.
Role of Phosphate and Nitrate for Aquarium Plants
Many aquarists wonder if aquarium plants absorb phosphates and nitrates and whether these two substances are harmful to them.
To answer– yes, aquarium plants absorb both these substances; in fact, they are essential to perform photosynthesis– the process through which plants produce their food. As a result, the plants grow and develop. These two substances are not harmful; on the contrary, when the level of phosphates and nitrates are low then required, the plants do not attain proper growth.
Every plant, including aquatic ones require nitrogen which they get from the soil and the water. This nitrogen, nitrite or nitrates are converted into proteins by the plants which is a prerequisite for their normal growth.
Regarding phosphate, is essential because this is the substance that helps plants to absorb different nutrients, such as nitrate or nitrogen, and convert them into easily absorbable forms. Other than this, phosphate helps plants develop different cell structures.
So, the role of phosphate can be summarized as
- Energy storage and transfer
- Cellular structure and function
- Root development
Likewise, the role of nitrate can be understood through the following points-
- Essential nitrogen source
- Chlorophyll formation
- Enzyme Activation
What about phosphate and nitrate for fish?
While phosphates and nitrates are beneficial for aquarium plants due to different reasons, the same doesn’t hold true for the aquarium fish. If these two substances go beyond the ideal range, they become hazardous for the fish. High concentration of both is considered toxic for the water creatures because they reduce the amount of dissolved oxygen, making it hard for the fish to breathe normally.
Here’s how a high level of phosphate can affect the well-being of fish-
- Leads to algae proliferation- One of the major reasons why your tank has excessive algae growth could be high concentration of phosphate. And, as the algae blooms, they compete with the aquarium fish for dissolved oxygen and nutrients, resulting in low oxygen for fish to breathe, especially during the night.
- Reduced water quality- When algae proliferate in the tank, less light penetrates into the water and becomes barely available for other aquarium plants. At the same time, the water gets cloudy, and water chemistry fluctuates. All of this stresses the fish and other organisms, like shrimp, etc., present in the tank.
- Increased biological load- As the excessive algae die, their decomposition further escalates the biological load and organic matter in the tank, which directly impacts the water quality.
The combined affect of algae bloom and deteriorated water quality cause physical stress to fish. It affects their immune system, making them susceptible to diseases.
In the same way, nitrate also contributes to algae bloom, which affects the water quality and fish’s health. Here’s how nitrate affects fish-
- Leads to health issues- When the nitrate level goes beyond the normal ideal range, it puts the fish under stress. As a result, the fish’s appetite reduces, they feel more lethargic and become susceptible to diseases.
- Damage to gills- When the level of nitrate reaches high, the gills of fish become susceptible to damage. As a result, it becomes hard for them to exchange gases and breathe properly.
- Reduced oxygen level- Due to algae bloom, the competition for oxygen and nutrients increases which again stress the fish and increase the chances of hypoxia in tank– a low oxygen level condition.
Therefore, dealing with these two substances, especially when their concentration increase, becomes essential.
What is the ideal range of phosphate and nitrate for aquariums?
When we want to maintain a balanced ecosystem in the aquarium, keeping an ideal range of certain substances, especially those who get fatal at high concentration becomes necessary. It will ensure that our aquarium plants, fish as well the water quality retain stable and suitable for the tank.
Below is the general guideline for phosphate and nitrate and freshwater and saltwater aquariums-
| Type of aquarium | Phosphate Level | Nitrate Level |
| Freshwater | 0.05 to 0.5 ppm | 5 to 20 ppm |
| Saltwater | 0.03 to 0.2 ppm | 5 to 10 ppm |
As the level of phosphate and nitrate go beyond these limits, you will encounter algae bloom, water quality issues, and deteriorated fish health.
Maintaining Phosphate and Nitrate Levels
Now that we know how important it is to maintain the ideal range of phosphate and nitrate in the aquarium, let’s find out the ways to keep their level under control so that neither aquarium plants nor fish get hurt.
- Keep an eye on their levels
Use test kits that reads the phosphate and nitrate level in the aquarium. Make sure you check their level regularly or at least once a week. If you experience something unusual, check the level immediately to take the further action. Also, maintain a record of your readings which will help to identify pattern and make informed adjustments.
- Water Changes
Changing aquarium’s water – typically 10 to 20% is a crucial step which can be done once a week. It will reduce the accumulation of phosphates and nitrates and maintain water’s freshness all the time. Make sure you use dechlorinated water so that unwanted chemicals do not enter the tank.
- Filtration
It is an important aspect in which mechanical filtration will keep the particulate matter out; biological filtration maintains beneficial bacteria that help convert ammonia into nitrite and nitrate, and chemical filtration targets specific substances such as phosphate and nitrate and absorbs them readily to maintain their level of.
- Nutrient Management
As we know, leftover or uneaten food particles break down to release various substances in water, so being mindful while feeding fish will help. At the same time, remove the uneaten food particles daily to avoid nutrient buildup.
- Add live plants in the aquarium
As we know that aquarium plants absorb phosphates and nitrates, adding a lot of them will help. They will absorb the excess of these substances for their own benefits. At the same time, live plants offer a lot of benefits to the aquarium water and fish. So, it will be a win-win for all.
Make sure that plants are well-maintained and you are not overcrowding the tank. Additionally, be mindful while adding fertilizer to these plants, as over-fertilizing will elevate the issue.
- Maintain substrate
Keep an eye on the debris on the substrate which leads to nutrient buildup. You can remove them while changing water with the help of gravel vacuum.
- Control algae growth
Since algae bloom can lead to increase in the concentration of phosphate and nitrate, keeping their growth in control is essential. For this, you can reduce the light exposure to around 8 to 10 hours a day because it is one of the major reasons behind algae bloom. Also, you can remove the algae manually to ensure they do not lead to water issues and compete for nutrients with fish and aquarium plants.
Final Words
When you are adding aquarium plants in your tank, having a thorough knowledge is essential to maintain their proper growth. In this regard. knowing the inside out about the major nutrients that develop in the aquarium is necessary.
Since nitrates and phosphates are essential for plant’s growth but their high level pose toxicity to the aquarium fish, maintaining the ideal range becomes crucial. So, following the above-mentioned tips will allow for a healthy tank.
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