All about fertilizers in a planted aquarium

There is more to caring for a flourishing planted aquarium than just picking out the appropriate plants and assembling the tank. In order to guarantee that your aquatic plants get the nutrients they require to grow robustly and colorfully, fertilizers are essential.

The health of your aquarium can be significantly improved by knowing the various fertilizer types and how to use them. Depending on the plants you keep and how your tank is set up, every type of fertilizer—from liquid to root tabs—has advantages and applications of their own.

We’ll go over the basics of fertilizing a planted aquarium in this post, so you can design an underwater garden that not only looks lovely but also helps your fish and plants thrive in a healthy ecosystem.

There is no universal fertilizer

While such bottles do exist, they are not appropriate for all aquariums. It would be great to have one bottle containing all the necessary additives, the dosing of which would lead to the successful maintenance of a planted aquarium.

All of the aforementioned macro- and microelements are present in this kind of fertilizer, which is referred to as complex.

Most often, these are aquariums with a low biological load / carbon dioxide supply / with active plant growth. Usually, all these factors coincide in one aquarium.

The aquarium needs to be supplied with macrofertilizers in a specific ratio: nitrates, phosphates, and potassium. This ratio is typically roughly 16/1/10 for N (nitrate), P (phosphate), and K (potassium) in these complex fertilizers. t.e. Potassium levels are roughly equal to nitrate levels, while phosphate levels are roughly ten times lower.

By giving plants the vital nutrients they require to flourish, fertilizers play a critical role in maintaining a healthy planted aquarium by guaranteeing vibrant growth and balanced water chemistry.

Why 16/1 is 10/1

The Redfield ratio is the ratio of nitrogen to phosphorus. However, if you take phosphate and nitrate fertilizer mono-solutions and create a ratio between them, you will obtain the Buddy ratio rather than the Redfield ratio.

In aquariums, we measure Nitrates and Phosphates using tests. In many articles, you could see the ratio 10:1 or 16:1, but this is the Redfield ratio (Nitrogen to Phosphorus).

In order for our values ​​​​of Nitrates and Phosphates measured by tests to be correctly converted to this ratio, a measured value of NO3 / PO4 is necessary multiply by 1.54. This will be the Redfield ratio.

For instance:

Nitrates (15 mg/l) and phosphates (1 mg/l) were measured in the water. Redfield ratio: not 15, but rather 23 (15: 1) * 1.54 = 15.

It is crucial to comprehend the values you are using as a result. Nitrogen and Phosphorus or Nitrate and Phosphate.

The range is 7:1 to 25:1. Depending on the particular aquarium you have. The ideal nitrogen to phosphorus ratio varies for each aquarium.

A universal fertilizer is therefore physically impossible. However! With an average nitrate/phosphate ratio of 16:1, complex fertilizers might be a good fit for you.

The likelihood that your aquarium will benefit from a complex fertilizer increases with the amount of biomass diversity and variety of plants present.

This is because different plant species have varying needs for nitrate and phosphate ratios. An 8/1 and a 25/1. I’ll give an illustration of a glossostigma aquarium in the Iwagumi style. For roughly a year, I was responsible for maintaining such an aquarium.

Without altering the quantity of phosphates and microelements supplied, I observed an instantaneous response when I increased the nitrate and potassium levels: glossostigma started to stretch and grow larger leaves right away. The stems rose to a height of 20 cm. Despite its active consumption, the nitrate concentration did not rise at the same time.

As a result, glossostigma consumes relatively little phosphates and a lot of nitrates. This means that if you use a regular complex fertilizer, you may experience a nitrate deficit and eventually total zeroing. In an aquarium like this, cyanobacteria, or blue-green algae, will eventually appear.

In these kinds of aquariums, nitrate mono-solution and complex fertilizer can be mixed together.

One might reasonably ask, Is it feasible to just add more complex fertilizer to such an aquarium in order to make up for the nitrate deficiency? You cannot, I repeat.

Because the other components of the complex fertilizer will start to accumulate while the nitrate is still being actively consumed. This is accompanied by the appearance of different kinds of algae, such as red (black beard) and green (filamentous).

In my opinion, complex fertilizers are:

By the end of the week, I advise using these fertilizers in aquariums with a range of plant biomass (five or more species) and a nitrate content of no more than five milligrams per liter.

Dosage

Depending on the aquarium’s initial conditions:

To such an aquarium, I suggest adding potassium and microelements. We’ll discuss them later.

If the nitrate value in your aquarium is, say, 5 mg / l and phosphates are outside the detection zone (on the smaller side) by the end of the week, then you can add a complex fertilizer to such an aquarium to avoid zeroing nitrates and phosphates.

Dosage depends on the water hardness. The softer the water, the easier the elements are absorbed. Thus, if your water is 0-4 gH and kN in the same range, add half the standard dosage. If water with a total hardness of gH above 8, most likely you will need 1.5x fertilizer application from standard dosage.

However, it is preferable to begin with a standard dosage and pay close attention to the plants’ behavior as well as the phosphate and nitrate readings. They shouldn’t begin to pile up.

Assume your aquarium contains 0.5 mg/l of phosphates and 5 mg/l of nitrates. If you change the water once a week, the measurement is taken on the third day following the change.

You cannot add complex fertilizer to such an aquarium, due to the fact that nitrates and phosphates are already present in your aquarium and they are accumulating, so why add them additionally? I recommend adding only potassium and microelements to such an aquarium.

If the volume of your aquarium does not allow you to add 1/2 of the standard dosage of complex fertilizer daily, for example, you have 15 liters of water, and the dosage is 1 ml per 60 liters of water, then add fertilizer every other day.

Therefore, even though they initially appear to be suitable for all aquariums, complex fertilizers that contain nitrates, phosphates, potassium, iron, and microelements are not suitable for all aquariums.

Two approaches: with the addition of phosphates and without their addition

Plants require nitrates, phosphates, potassium, iron, and microelements for growth, as I mentioned previously.

As the pioneer of aquascaping, ADA was the first to consciously refuse to add phosphates to water, making them a leader in the field.

They used sintered soil as the foundation for their soil, Soil Amazonia. Apart from their other characteristics, aquasoils—many companies have started to actively cultivate them—absorb phosphates from water.

• Their initial content at the time of launching an aquarium with Soil soil is around 0.05 mg / l.
• ADA believes that this is a necessary and sufficient amount of phosphates in a planted aquarium due to the fact that over time it will accumulate in the soil due to fish waste and there is no need to add them additionally.

• So, it turns out that according to the ADA system, Potassium and Microelements are dosed at the start of the aquarium (first month).
• Iron is dosed as needed: insufficiently juicy, insufficiently red or green plants.

ADA fertilizer dosage at first 1/20,000 liters of water. in gH-indicating soft water

We now categorize aquariums according to their water type (soft or hard), fish population (big or small), use of soil (using or not using it), and phosphate addition (adding or not adding) in the system.

Why is it that understanding this is so crucial?

• If we have soil that has the properties of accumulating phosphates, then using water tests, we will always see distorted values.
• After 4-5 hours after applying fertilizers, phosphate should definitely be at a value of 0 mg / l. At the same time, this does not mean that there is no phosphate in the soil.

But, based on experience, it is possible to use fertilizers containing phosphates on Soil soils. In cases where we see signs of phosphate deficiency in plants, or when we know in advance that the plant species we have planted require higher phosphate concentrations: such plants include, for example, Marsilea.

"Leaching" is a concept used in soil science. This is phosphates returning to the water from the soil, to put it simply. Because phosphates are released from the soil into the water, tests that alter only the water’s hardness will reveal varying levels of phosphates in the water.

Type of Fertilizer	Purpose
Liquid Fertilizers	Provide essential nutrients directly to plants through the water column.
Root Tabs	Supply nutrients to plants that take in nutrients through their roots, like swords and crypts.
CO2 Supplements	Boost plant growth by increasing the availability of carbon dioxide, which is vital for photosynthesis.
Micronutrients	Deliver trace elements like iron and magnesium, crucial for healthy plant growth.
Macronutrients	Provide key nutrients such as nitrogen, phosphorus, and potassium, essential for plant health.

Choosing the correct fertilizers is crucial to keeping a planted aquarium healthy. You can create an environment that is conducive to the growth of both fish and plants by learning about the needs of your plants and the particular nutrients they require.

Nutrient deficits and the growth of algae can be avoided with routine fertilizer monitoring and dosage adjustments. It all comes down to striking the ideal balance for your particular configuration.

Recall that maintaining a healthy planted aquarium benefits your aquatic life’s general health in addition to its aesthetic appeal. You can have a colorful, flourishing underwater garden with the appropriate fertilization strategy.

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