In conversations about aquariums, the Redfield ratio is frequently brought up, particularly when it comes to balancing nutrients for aquatic plants and algae. This ratio, which was first created by oceanographer Alfred Redfield, describes the ideal ratio of phosphorus (P) to nitrogen (N) in water. To put it simply, it’s a recommendation that, in order to promote balanced growth in aquatic ecosystems, there should be 16 parts nitrogen to 1 part phosphorus.
Some aquarium enthusiasts consider the Redfield ratio to be an infallible method for controlling nutrient levels and averting algal blooms. They contend that preserving this particular equilibrium encourages the growth of healthy plants while aiding in the control of algae. Not everyone, though, is in favor of this strategy. The Redfield ratio’s applicability in controlled tank environments, such as aquariums, where conditions differ greatly from the open ocean where it was first observed, is a topic of much discussion among aquarists.
The main source of the debate is the fact that every aquarium is different, with different kinds of plants, different numbers of fish, and different water parameters. Some contend that the Redfield ratio should not be strictly followed because it oversimplifies nutrient management and that other variables, like light intensity, CO2 levels, and the unique requirements of various plants, are far more important. As a result, there are continuing debates and contrasting views regarding the usefulness of the Redfield ratio as a guideline versus its status as a myth in the aquarium community.
| Aspect | Explanation |
| What is the Redfield Ratio? | The Redfield Ratio is a guideline for the balance of nitrogen to phosphorus in aquatic environments, typically set at 16:1. It"s used to assess nutrient levels for optimal growth of aquatic plants and algae. |
| Does it work? | Some aquarists find it useful for managing nutrient dosing in planted tanks, but its effectiveness can vary depending on specific tank conditions and goals. |
| Why do people argue? | Debate exists because the ratio is not one-size-fits-all; different tanks have unique needs, and strict adherence may not always result in the best outcomes. Critics argue it oversimplifies complex nutrient dynamics. |
- History of the issue: what is the Redfield ratio and what does Liebig have to do with it
- Liebig"s law in simple terms
- How it works in practice
- Two main arguments of criticism and responses to them
- Answers to frequently asked questions
- Video on the topic
- Fertilizers in the aquarium according to the Redfield ratio
- Algae appeared – the Redfield ratio
- What is the Redfield ratio and why is it needed
History of the issue: what is the Redfield ratio and what does Liebig have to do with it
Oceanographer Alfred Redfield listed the elemental atomic ratios in 1934:
- carbon, nitrogen and phosphorus in marine plankton – C:N:P = 106:16:1;
- nitrogen and phosphorus in seawater – N:P= 20:1 (first version), N:P= 16:1 (corrected version).
Redfield also pointed out that changes in the elemental ratios in water have an impact on the development and makeup of algae. For blue algae, higher phosphorus content is good; for green algae, higher nitrogen content is good. The Atlantic, Indian, and Pacific oceans as well as the Barents Sea were the locations where data were gathered. As a result, concerns regarding the sample’s representativeness cannot be raised, and the correlation that was found is not the result of chance or statistical error.
Algal growth and composition are impacted by changes in the elemental proportions in water.
Fantastic, detractors will say; Redfield is a nice guy who made a significant scientific discovery, but what good does this do us? Now is the moment to recall Liebig’s limiting factor.
One of the fundamental tenets of ecosystem development was expounded by Justus von Liebig in 1840: an organism’s most significant characteristic is its greatest deviation from the norm.
Liebig"s law in simple terms
Assume that our only resources are food and water. There are then two undesirable choices:
- there is water, no food – the organism dies of hunger, and quenching thirst cannot help here;
- there is food, no water – dies of thirst, because food is not able to replace water.
Giessen, 1840: B. Trautschold Liebig’s laboratory
In the first scenario, insufficient water is the limiting factor, and in the second, food shortages are the blocking factor. The idea is applicable to a wide range of variables.
There is only one primary mineral, found in a small reserve, that restricts plant development. This idea of restriction can be visualized as a "Liebig barrel," a symbolic barrel with each bar standing for a component.
Regarding an aquarium, this indicates that a plant cannot physically make up for a lack of one element by sacrificing other elements. A critical lack of any component causes the plant to stop taking in other nutrients completely, eventually become ill, and eventually die. Furthermore, algae—blue-green "parasites" and green "dots" that detract from the aquarium’s aesthetic—may grow on the nutrients that the plant is unable to absorb.
The ideal ratio of nutrients—nitrogen and phosphorus, in particular—for the growth of algae and aquatic plants is known as the Redfield ratio. While this ratio makes sense in theory and in natural ocean environments, it doesn’t always translate perfectly to the controlled conditions of home aquariums, which is why aquarium enthusiasts frequently debate it. Whether the Redfield ratio can effectively stop algae growth or if it oversimplifies the intricate nutrient requirements of various species in a tank are the usual points of contention. Though there isn’t a one-size-fits-all approach, aquarists can make better decisions by understanding its guiding principles.
How it works in practice
There is a method for figuring out the atomic ratio using fertilizer mass. Redfield’s data is thought to be closest to the ideal proportion; its values are indicated in white. The amounts of fertilizer that cause the corresponding algae to grow are blue and green.
The Redfield ratio is employed and recommended by certain UDO manufacturers, while it is criticized by others, and still others choose to remain silent.
Two main arguments of criticism and responses to them
Argument 1. A phytoplankton-related scientist found the ratio in seawater. Utilization in a standard freshwater aquarium appears improbable.
What matters is how it functions; its appearance is irrelevant. De facto, plants do best in the range of 10:1 to 20:1 nitrogen to phosphorus ratios. Aquarists have tested this for many generations.
What’s the connection between it and Redfield? It’s possible that aquarists attempted to use his ratio as an experiment; the outcome was positive and quickly spread. Maybe they were trying to find a way to remove the algae without damaging the plants, so they used this ratio to help them in their initial attempts.
Kindly take note! Alternatively, it’s possible that aquarists were guided by similar proportions long before Redfield penned his scientific works and that UDO manufacturers capitalized on his name. Hardly anyone is aware of the actual circumstances.
Argument 2: Since plants get their nitrogen and phosphorus from sources other than fertilizers, it is practically impossible to maintain the ratio exactly.
That’s a fair observation. In fact, it’s important to keep an eye on the water’s composition in the aquarium in addition to adding elements in the appropriate amounts. Additionally, fish food, water, and soil provide nitrogen and phosphorus to plants.
It is imperative to keep an eye on the aquarium’s water composition.
As a result, it’s essential to routinely test the water, monitor any alterations in the ecosystem, and, if required, adjust the duration of the day and the UDO introduction plan. Nobody, however, asserted that keeping an aquarium in the Redfield proportion is all that is required for upkeep.
The function of fertilizers in aquarium plants’ lives
Answers to frequently asked questions
Based on the quantity of plants. You must fertilize more actively the more of them there are per cubic centimeter.
Decrease the amount of fertilizer while keeping the same ratio, and/or shorten the day to 6–8 hours.
Everything is unique and contingent upon the aquarium. To ensure that there is neither an excess nor a shortage of elements, you can add a little bit each day or once every three days.
Through phosphorus. If it’s insufficient, you’ll need to supplement it with 10–12 times as much nitrogen. If not, nitrogen will turn into the blocking element when it becomes saturated with phosphorus.
Maybe fertilizers are not needed if fish, water, and soil provide plants with nitrogen and phosphorus?
Indeed, it is feasible to do this. For this reason, you should wait to add parole to the new aquarium and instead observe how the ecosystem is growing. Fertilizers won’t be needed very soon if there are lots of fish and few plants.
It’s understandable why the Redfield ratio has generated so much discussion in the aquarium community. Although it’s not a universally applicable solution, the nitrogen to phosphorus ratio can provide a helpful guideline for preserving nutrient balance. The particular goals, species, and conditions of each aquarium can have an impact on the best way to manage nutrients.
While some aquarists contend that the Redfield ratio doesn’t always apply to closed systems like home aquariums, others find that adhering to it helps keep algae in check and supports plant growth. Flexibility is often essential due to the inherent variations in fish waste, plant requirements, and water chemistry. Rather than following a strict ratio, it’s critical to pay attention to the unique requirements of your aquarium and make adjustments as needed.
In the end, the Redfield ratio’s significance comes from its use as a foundation for comprehending nutrient dynamics. Regardless of whether it suits your setup, it emphasizes how crucial it is to keep an eye on and modify nutrient levels in order to create a balanced and healthy aquarium environment. Reminding us that aquascaping is both a science and an art, requiring patience, observation, and a willingness to adapt, are the ongoing discussions surrounding the Redfield ratio.
