Optimal Aquatic Growth in Your Planted Tank: Fertilizer and Other Factors

April 03, 2022 5 min read 0 Comments

Owning an aquarium is like having a little underwater garden in your home. Most new aquarium owners focus on the exotic sea creatures they want to keep, but that is only half of the living organisms that will reside in your tank. You must also consider the aquatic plant life you want to incorporate in the underwater environment. What type of plants do you want? What type of upkeep can you commit to? What structures will the plants be able to grow around?

It is critical to plan for the layout of the aquatic plants as well as how many you plan to keep, as these factors will change the technological and nutritional requirements of your little ecosystem. Your fish and other sea creatures will thank you for providing a nutrient rich environment for them to live in. 

What Do Aquatic Plants Need to Thrive?

Not unlike your terrestrial plants or human beings, aquatic plants require a steady supply of high-quality nutrients to grow healthy and strong. If all the necessary micronutrients and macronutrients aren’t supplied to the aquatic plants, they refuse to grow. Malnourished aquatic plants will grow with deformities such as small twisted leaves, large holes, and rotting in the older leaves.

There are four main factors to focus on in order to keep the aquatic plants in your aquarium healthy and happy. These four factors form the basis for a well-balanced ecosystem that will lead to healthy, beautiful plant growth.

1. Light

All plants need light for photosynthesis, including aquatic plants. Oftentimes new aquarium owners are advised to focus on and invest in several quality lights in order to facilitate aquatic plant growth. They will get expensive lights, set them up, and then call it a day, which inevitably leads to poor plant growth. Having a good lighting set up is important, but it is only one of the factors that need to be considered. 

If you are new to the world of planted aquariums, it might be in your best interest to look into plants that have lower light requirements. Some aquatic plants are much more capable of surviving with less light and will prove to be much easier to maintain in the long run. If you have ever visited an aquatic nursery, you may have noticed the “traffic light system” that is used to identify which plants are easier than others to grow. For example, “Green” means the plants are easier to maintain, such as mosses and fern. “Yellow” plants are easier to maintain but not totally mindless. “Red” offers plants like those that have reddish stems, which tend to need a lot more light and care.

2. Carbon Dioxide (CO2)

Carbon dioxide is essential for cultivating fast-growing aquatic plants. Aquatic plant health is significantly improved by the addition of carbon dioxide into your ecosystem. When you fertilize your planted tank with carbon dioxide, you are supplying your plants with an element that is usually lacking in aquariums that do not have a built-in carbon dioxide injection system. Carbon dioxide helps plants utilize the minerals in the environment for growth. Using carbon dioxide will help your plants utilize nutrients and minerals even in low light conditions.

Some people choose to build their planted tanks without a carbon dioxide system because of budgetary concerns. The good news is there are several options for both high and low budget builds. If you choose not to inject co2, then make sure  you limit light, otherwise algae will likely be an issue for you.  

3. Balanced pH Levels

In general pH isn’t terribly important with respect to plants. There are some plants that prefer soft ware more acidic environments; however it is far more important to maintain a stable pH than a specific level.

4. Fertilizers & Nutrients

Fish food and waste will introduce some, but not all, nutrients that aquatic plants need into the ecosystem, but a smart aquarium owner will use a well-balanced fertilizer to ensure optimal aquatic plant growth.  

The chemical elements necessary for healthy plant growth can be grouped into two major categories: macronutrients and micronutrients. Macronutrients are needed in larger quantities while micronutrients are sufficient in smaller quantities. 


Macronutrients make up roughly 96% of a plant’s mass. Many of the basic building blocks for plants come from air, water, hydrogen, and oxygen. The most common macronutrients found are Nitrogen, Phosphorous, Potassium, Calcium & Magnesium, Sulfur. Your plants use ten times more carbon by mass than all the other macronutrients combined. Aquatic plants take these in nutrients through the water column.

If you plan to have a tank with a lot of plants, you’ll need to focus on your nitrogen, phosphorus and potassium levels. Some of these compounds are created naturally in the aquarium when microorganisms break down fish excrement, fish food, and dead plants. This process is often not enough to support a large quantity of plants and requires the use of a macronutrient rich fertilizer.


The main function of micronutrients is the promotion of growth hormones, photosynthesis, cell development, plant metabolism, and nitrogen assimilation. Micronutrients are used in very small quantities, especially compared to macronutrients.

The most common micronutrients used by plants are Iron, Chloride, Boron, Manganese, Zinc, Copper and Molybdenum. Of all the trace elements, aquatic plants mostly require iron, as it is responsible for the green color of the leaves. All necessary micronutrients should be found in a well-rounded fertilizer.

Natural Waste Isn’t Enough

When aquatic plants get access to all their nutritional needs, they can grow more densely and exhibit better coloration. Your aquarium is an enclosed environment. Unlike a natural environment, there is no built-in cycle of nutrient replenishment that returns nutrients back to the soil. Some aquarium substrates can provide nutrients for a while, but all substrates eventually deplete their resources.  

Some tanks completely depend on natural waste as fertilizer and are known as “no dosing” tanks. In most of these planted tanks, necessary elements such as potassium and iron are often deficient. Some organic waste doesn’t decompose completely, leaving behind several by-products. Too many by-products and elevated levels of organic can lead to algae. While some tanks can survive with the “no dosing” approach, they rarely have the best growth or coloration. Dosing fertilizer can make a significant difference in your aquatic plant’s health

Liquid Fertilizer vs. Dry Fertilizer

When it comes to choosing a fertilizer, there are two main types: liquid fertilizers or dry fertilizers. Chemically speaking, most dry and liquid fertilizers are the same. The big difference between the two is price, convenience, and accuracy of the product. Buying a dry fertilizer is significantly cheaper. 

This is where liquid products can be better, as they come premixed in the correct concentrations. Liquid fertilizers are heavy and thus more expensive to ship, thus more expensive overall. When choosing your next fertilizer, look for all-in-one fertilizers that cover nutritional angles.

What are the Consequences of a Lack of Nutrition?

When plants do not receive the nutrients they require, growth begins to slow. For plants with roots, energy will be channeled to root growth in search of nutrients in the substrate layer. Depending on what kind of nutrient is lacking, a mix of symptoms can occur to indicate the culprit. Leaves becoming paler, new shoots taking on a whitish hue, stems appearing thin with small leaves; these are all indicators for lack of nutrition.Weak and unhealthy plants are the number 1 cause of algae. Feeding plants regularly to ensure their good health is critical to deter algae. Dosing only when deficiencies occur is not a good strategy, as the plant will already be stunted and problems like algae would already have spawned. Rather than wait for deficiencies to manifest, an easy way to avoid deficiencies in general is to have a regular dosing regimen. Most successful planted tanks follow this approach.