How to Balance a Planted Tank?

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It’s a fact that planted aquariums tend to fail more often than non-planted ones. The reason for that is simple – plants are living beings that require special care, just like fish do.

It’s easy to overlook this point, though, because plants don’t swim, don’t have mouths, and don’t move much. They just stay there.

So, today we’ll look into planted aquariums to understand how to optimize your aquatic setup to cater to your plant’s needs.

Your plants will return the favor, which is what makes this point so important. So, let’s get into it!

Balancing Your Planted Tank

There are 3 primary resources to consider when it comes to creating a self-sustainable planted tank:

  1. Lighting
  2. Nutrients and
  3. CO2

These are not the only factors, but they’re the most important, and we’ll discuss why shortly.

– Lighting

All plants, aquatic or otherwise, require sufficient lighting to thrive. That’s because plants use CO2, nutrients, and light to perform photosynthesis, allowing the plant to support its physiological functioning.

While the whole lighting concept sounds simple in theory, it’s the practice that makes or breaks the experience.

Plants require around 8-10 hours of lighting per day, followed by 12-14 hours of darkness/low-light conditions.

But how much lighting do plants actually require in terms of intensity? This is us entering confusing and tricking territory because different plants require different light levels.

Here’s what you should know regarding this topic:

  • The dangers of too much light – I understand the appeal of exposing your tank to more intense light sources. The bright light really makes all the coloring shine and sparkle through the tank’s glass. The problem is that excessive lighting is tightly correlated to algae bloom. Algae will spread fast, covering the plants’ leaves and inhibiting their ability to perform photosynthesis. This is a problem.
  • Different light levels for different plants – Some plants are more light-sensitive and can thrive in low-light conditions. These include java moss, java fern, anubias, dwarf rotala, etc. Others demand high light conditions like scarlet temple, monte Carlo, ammannia gracilis, and many others. The latter are more fitting for high-tech aquariums with bright lighting. So, choose your plants carefully.
  • Fish don’t need bright lights – Many people use brighter lights because they think that fish need them. Others do it because the excess light brings out the colors in fish. Both are unnecessary because most tank fish will do just fine in low-to-moderate lighting conditions.

So, how should you solve the lighting problem? The solution lies in tweaking the tank’s lighting intensity gradually. You should set up your lighting intensity to 30% of the official recommendation.

Get a common aquarium light source and drop the intensity to about 30-40% max, depending on your plants’ requirements.

Give it some time and see how your plants react to the light source. If the leaves remain low and the plant doesn’t appear to change their position over the course of several days, up the intensity a bit.

Plants will always rotate their leaves in the direction of the light source.

The idea is to find the ideal sweet spot between the plants and the algae’s requirements. You want the light intensity to be sufficient for plants but insufficient for algae.

This isn’t the only strategy to use since we’ll also discuss the role of CO2 in combating algae, aside from tweaking the light intensity.

– Nutrients

This is both a simple and a tricky topic. Plants require a variety of nutrients which require carefully balanced.

Especially in a closed aquatic system like an aquarium that doesn’t benefit from the perks of a free circulation of nutrients like an open system.

To understand the topic better, consider the fact that plants require 2 types of nutrients, macro, and micro. Macronutrients are 3: nitrogen, potassium, and phosphorus.

Plants need these in larger quantities throughout the day. Some examples of micronutrients include boron, iron, copper, calcium, zinc, and others, which plants only require in smaller quantities.

The main problem is that nutrient deficiencies in plants can be more intricate, let’s say than you might expect.

In other words, a plant lacking a specific nutrient may not be able to process another, for instance. This can lead to more than one nutritional deficiency.

When it comes to balancing your plants’ nutritional requirements, consider these tips:

  • Get the right plants for the job – Some plants require different amounts of potassium than others, for instance. So, adding more potassium to the tank to fulfill one plant’s needs can affect the other plant. Ensure that all of your plants demand similar nutrients to prevent that.
  • Mind the plants’ size and growth rate – Larger, faster-growing plants will consume more nutrients than smaller, slower-growing ones. Pairing the 2 types will always be detrimental to slow-growing plants since fast-growers will eat all of the nutrients. So, they will starve and develop nutrient deficiencies along the way. Make sure that your plants have similar growth rates and nutrient requirements to prevent imbalances in this sense.
  • Use fertilizers with caution – Always measure your fertilizers carefully. Add too much to the tank, and the fertilizers will also feed the algae. Only provide your plants with the right amount of fertilization and nothing more. Liquid fertilizers are especially dangerous in this sense, as they promote algae bloom even in moderate quantities.

– CO2

Plants use CO2 around the clock during the day as part of the photosynthesis process. It’s important to note that different plants have different CO2 requirements, but they all need it.

This means that some aquariums demand CO2 injections, especially high-tech systems with a lot of fast-growing plants.

CO2 injections are great for such systems because they promote plant growth and inhibit algae at the same time. But the same CO2 injections are rather unsafe in fish-filled environments because fish don’t breathe CO2.

More importantly, CO2 displaces oxygen molecules from the water column, making it more difficult for fish to breathe.

Plus, plants consume oxygen and produce more CO2 during nighttime, exacerbating the problem to life-threatening levels.

It’s not uncommon for fish to suffocate during nighttime because of it.

Signs of Nutrient Deficiency in Plants

All plants are prone to nutrient deficiencies, no matter whether they’re land or aquatic plants.

When that happens, they will display specific signs, depending on the nutrient they’re lacking.

Here’s what I mean by that:

  • Nitrogen – Stunted growth and yellowing of the leaves due to the plant no longer being able to adjust its chlorophyll levels.
  • Phosphorus – Browning or red coloration in the lower leaves, closer to the base of the stem. The plant will also exhibit signs of necrosis and death in severe cases.
  • Potassium – Leaves display yellow margins and will shrink and curl with time. The plant also showcases hindered growth and will eventually die if the issue isn’t addressed.
  • Calcium – Hindered growth and malformed leaves.
  • Magnesium – Losing leaves and leaves displaying dark veins and yellowing.

Unfortunately, many symptoms overlap, causing confusion in relation to the causes. This is why you need a water tester kit to pinpoint the issue correctly.

Substrate is Important

The tank’s substrate is paramount to the plants’ health over time. We’re talking primarily about rooted plants since these get their nutrients from the substrate-only.

In this sense, consider the following:

  • Inert substrates require additional fertilizationSand and gravel are the most popular substrate choices. The problem is that these are inert substrates; in other words, they are devoid of nutrients. So, you need to utilize root tabs to give your plants the nutrients they need. Fast-growing, larger plants demand more root tabs than smaller, slower-growing versions.
  • Consider substrate mixes – Aquasoil is generally the most nutritious substrate for rooted plants, but this isn’t the only option available. You can also mix enriched soil with other forms of substrate like peat moss or crushed corals for a plus of calcium and other nutrients.

You can also get different types of Fluval stratum, designed specifically for aquarium plants and shrimp.

There are different versions, depending on the nutrition content and where you plan on using them.

Using Water Test Kits

Water test kits are key to verifying water quality, scanning for various environmental contaminants, and checking the CO2 levels in the water. The better pieces available on the market scan for dozens of contaminants and heavy metals to inform you when water quality has gone down.

The ideal water test kit should:

  • Be cheap
  • Provide relevant results as fast as possible (preferably under the 10-minute mark)
  • Scan the water for as many contaminants as possible
  • Inform you of the CO2 levels in the water
  • Test the water for various nutrients like iron, magnesium, and others

When is Your Tank Balanced?

By ‘balanced,’ you should read: the correct proportions of light, CO2, and water nutrients.

Plants need all these 3 to remain healthy and grow properly over time. The answer is that there’s no specific value to consider.

The amount of light, CO2, or dissolved nutrients depends on your plants’ requirements and how many plants you have. The testing kit will help you in this sense.

It’s normal to mess things up at first, so expect your plants to experience nutritional deficiencies or face algae overgrowth in the beginning. To achieve the ideal water balance, you must first test and play with different indicators along the way.

Tweak the CO2 levels a bit, low or increase light intensity, and add one or more nutrients based on what your plants require.

The water test kit will eventually help you achieve the balance you’re looking for.

Important: Change One Thing at a Time

Don’t change too many parameters at once. Plants are living beings that react to their environment in real-time.

Changing too many parameters at once can overwhelm the plants and cause them to fall back.

If you need to change anything in terms of temperature, lighting, CO2, or dissolved nutrients, do it one at a time.

Then allow the plants 2-3 weeks to adapt to the changes before taking the next step.


A planted tank comes with additional challenges compared to a plantless one. But it also comes with a lot more benefits along the way.

Ultimately, creating a well-balanced planted aquarium comes down to science and precision. Use the tips and advice I’ve provided, and you can’t go wrong.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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