Can You Use Fish Emulsion in Hydroponics? (Pros and Cons)

If you love organic gardening and are looking for a quick and easy way to provide essential nutrients and growth hormones to your hydroponic plants, fish emulsion could be a good choice.Wondering if you should try it too? Then, let my experience with its benefits and drawbacks help you!

Generally, fish emulsion in hydroponics is used because it is organic, mild, nutrient-rich, activates plant growth hormones, and reduces waste. However, it has some disadvantages, including its high price, unpleasant odor, need for frequent reapplication, and it violates vegetarian/vegan principles.

I’m sure you have so many questions about using fish emulsion in hydroponics. So, at the end of this article, I prepared some questions on factors you have to consider before purchasing this organic fertilizer. For now, just like a fish, let us dive in!

Should You Use Fish Emulsion in Hydroponics?

Using fish emulsion in hydroponics is a recommended due to its nutrient composition. It is a thick and heavy liquid fertilizer that is well-known for providing hydroponic plants with proteins, amino acids, and oils. However, drawbacks such as bad odor should be considered.

Before we start with a whole discussion, let us first know what fish emulsion is.

A fish emulsion is a fertilizer made from one or more parts of a fish. This may be internal parts, external organs, or a whole fish!

How does this help plants?

These fish parts provide hydroponic plants with a significant nitrogen boost, as well as phosphorus and potassium. These are three of the most essential elements needed by the plants.

   To know more about this, head to our article on 3 hydroponic nutrients.  

Why is this important?

Lack of nitrogen is one of the leading causes of plant death, particularly in hydroponic systems. Nitrogen is also a valuable element in leafy hydroponic plants such as lettuce, kale, bok choy, and spinach. This is because it is responsible for leaf growth, color, and development.

This is why fish emulsion is best for leafy veggies and herbs!

5 Pros of Using Fish Emulsion in Hydroponics

Because of its organic, mild, nutrient content, effect on beneficial microorganisms and growth hormones, and waste reduction, fish emulsion is highly beneficial in hydroponic systems.

1. Organic

Since fish emulsion uses environmental wastes from fishes, it is better than using synthetic fertilizers. Thus, commercial hydroponic farms that use fish emulsion can apply for an organic certification and label their produce as organic.

Organic Choice: Fish Emulsion
Organic Choice: Fish Emulsion

If you want to go organic with your hydroponic gardening, fish emulsion is a good option! Some organic farmers also combine it with seaweed extract.

2. Mild Fertilizer

Fish emulsion is suitable for beginners due to its mild concentration and low nutrient ratio. Most hydroponic nutrients still require computation or conversion, which may deter gardeners from using them.

Analysis of nutrients in fish emulsion revealed that its nutrient ratio is 2:4:1 for nitrogen (N), phosphorus (P), and potassium (K), respectively. With this ratio, we can say that the fish emulsion fertilizer is mild. This also means that there is a very low risk of damaging or burning the leaves of your hydroponic plants.

As a consequence, you will need to feed your hydroponic plants frequently. If you are hesitant or inexperienced with synthetic or hydroponic fertilizer, fish emulsion fertilizer is a good option because using it is straight-to-the-point.

More information on how to use fish emulsion will be provided as we move forward.

3. High Nutrient Content

Analysis showed that a typical fish emulsion may contain a 2:4:1 ratio of nitrogen (N), phosphorus (P), and potassium (K). Micronutrients such as magnesium, chlorine, sulfur, calcium, and sodium have also been identified.

In a hydroponic system, using fish emulsion will help nourish your nutrient water. It can be applied as a supplement to other hydroponic nutrients, if you are growing several plants. This is more appropriate for commercial gardening in nutrient film technique (NFT) hydroponics.

But in smaller systems, such as deep water culture (DWC), diluted fish emulsion solution can be used alone in the nutrient water.

You might ask, “how do you properly dilute fish emulsion?” This is a question that we will answer later!

4. Precursor for Plant Growth Hormones

Fish emulsion activates the production of plant growth regulators such as auxins, cytokinins, and gibberellins. These are hormones responsible for controlling development of leaves, flowers, and fruits of hydroponic plants.

Plant growth hormones may be a foreign term to you right now. But consider them this way—they are comparable to the four elements of water, fire, earth, and air.

These elements play distinct roles in our world, correct? Their combined forces, however, help in human progress.

Let us dig deeper on the examples of plant growth hormones mentioned above.

  1. Auxins. They primarily regulate growth by increasing cell size. They can act as both growth stimulators and growth inhibitors for roots, stems, and buds.
  2. Cytokinins. They play a role in plant cell division, cell enlargement, senescence (plant aging), and growth.
  3. Gibberellins. They control cell length and division in plant stems. They also stimulate the making of ribonucleic acid (an important chemical for plant genetics) and protein (a macromolecule responsible for growth) in plant cells.

5. Reduces Wastes

Using fish emulsion reduces waste since it turns fish scraps into fertilizer. This is beneficial for home-based hydroponic gardens since one can make use of wastes from the kitchen!

Most of the time, fish wastes are just discarded. Thus, turning them into fish emulsion is an efficient way towards harmonious resource management.

In a nutshell, we culture fishes, consume them, turn their body parts into fish emulsion, and nourish our hydroponic plants with the derived nutrients from them.

4 Cons of Using Fish Emulsion in Hydroponics

A higher price compared to other hydroponic nutrients, unpleasant odor, the need for reapplication, and being against vegan principles are drawbacks of using fish emulsion in hydroponics.

Find out more details below!

1. More Expensive Than Other Fertilizers

Fish emulsion market prices are relatively higher at 35 USD .More specifically, it is more expensive when compared to liquid hydroponic solution counterparts priced at 30 USD and below.

This 1-gallon fish emulsion available on Amazon is priced at 39 USD.

This other option costs 35 bucks for a 1-gallon fish emulsion on Amazon.

Compared to Other Alternatives

Powdered Hydroponic Nutrients. This one costs 40 bucks but can be dissolved in water and can last long. I have mine for a year and the powdered nutrients are still good!

Liquid Hydroponic Nutrients. This 1 gallon of liquid hydroponic nutrients only costs 30 dollars!

   Learn more about the difference between these nutrients in our article on 3 hydroponic nutrients.  

2. Has Unpleasant Odor

Because fish emulsion is made from fish parts, an unpleasant odor might be highly undesirable for hydroponic gardeners. This may be more concerning for people who have set up their hydroponic systems indoors, in an enclosed space with limited ventilation.

This factor is somehow expected since a fishy smell is inherent with the fish emulsion ingredients. Because it is made from fermented fish, it smells strongly putrid.

If you use it excessively or in low dilution, it will probably irritate the people around you—may it be your family or a neighbor! Thus, it is best to apply fish emulsion when there are no other people around.

Furthermore, it can attract flies and cats into your hydroponic garden.

3. Needs Frequent Reapplication

Fish emulsion is a relatively weak solution if compared to other hydroponic solutions available in the market due to its low nutrient ratio. Thus, it gives the gardener additional work to reapply it twice a week.

Reapplying Fish Emulsion
Reapplying Fish Emulsion

One may ask, “can I just add more fish emulsion and apply once a week?” or “can I reduce the dilution instead of reapplying?”

Well, the major disadvantage that we are fighting right here, is the bad odor of fish emulsion. Once you reduce the dilution, the unpleasant smell is exemplified. Thus, reducing dilution or adding more fish emulsion are not advised.

4. Against Vegetarian/Vegan Principles

Using fish emulsion in hydroponics might be against people upholding a vegetarian or vegan lifestyle. This is because animals are hurt along the process of food production.

Considering this, if you are a vegetarian or vegan hydroponic grower, you may opt using dry or liquid hydroponic nutrients that are available in the market. But, if you want to stay organic, using liquid seaweed extract is also a great option!

3 Questions to Ask Before Using Fish Emulsion

Questions on garden scale, economical value, and odor must be asked before deciding to buy fish emulsion.

Now, let’s find out if using fish emulsion for your specific hydroponic setup will be a good choice!

1. Is it more practical to use fish emulsion than the natural hydroponic nutrients?

If you are growing leafy vegetables on a small scale, then using fish emulsion is a good choice for you.

However, you still need to ask yourself if there are other cheaper and more efficient alternatives such as liquid hydroponic solution or dry nutrients. Typically, these options are higher in concentration and nutrient ratios.

2. Can my family and neighbors handle the bad odor?

This is a decision that must also be consulted with your family and neighbors. Using fish emulsion can produce disturbing odors that could irritate the people around your garden.

3. Am I growing small-scale or large-scale?

Fish emulsion is used as a sole component when growing in a small-scale garden, whereas it is used only as a supplement in large-scale gardens e.g. commercial lettuce farms.

This must be asked for you to know just how much you will need. It will let you see if you would need a few more gallons of fish emulsion or just a little.

How to Use Fish Emulsion in Hydroponics

Dilution is key in using fish emulsion in hydroponics, regardless of the type of application used by a gardener.

Dilution in Using Fish Emulsion
Dilution in Using Fish Emulsion

Fish Emulsion as Foliar Spray

  1. Dilute 1 tablespoon of fish emulsion for every gallon of water.
  2. Place the solution into a spray bottle.
  3. Spray it on your plants twice a week.

Fun Fact: Using fish emulsion as a foliar spray is best for leafy veggies such as lettuce, spinach, bok choy, and kale. This is because the nutrients from the fish emulsion can be absorbed by the leaves.

Fish Emulsion as Hydroponic Water Additive (2 Ways)

1. For large-scale gardening:

  1. Dilute 1 tablespoon of fish emulsion in a gallon of water.
  2. From the diluted solution, get a teaspoon and mix it with your hydroponic solution.

2. For small-scale gardening:

  1. Measure 1 teaspoon of fish emulsion.
  2. Mix this amount to every gallon of water your reservoir has. For example, 4 teaspoons for a 4-gallon hydroponic reservoir.


Can you make DIY fish emulsion?

Fish emulsion can be made using fish scraps, organic materials (e.g. dried leaves, coco coir, or saw dust), and water. Layer the solid materials until it reaches ⅔ of the bucket. Fill the bucket with water. cover with a lid, and let it ferment for a month. After this, strain the mixture. The harvested solution can now be used as a fish emulsion.

Can I use fish emulsion with other organic ingredients?

Fish emulsion can be used alongside seaweed and blood meal for hydroponic lettuce and tomatoes. For each gallon of water, add 1.5 teaspoons fish emulsion, 1.5 teaspoons liquid seaweed, and a teaspoon of blood meal. However, half a teaspoon of blood meal is recommended for fruiting veggies and herbs.

Are fish emulsions for soil also applicable for hydroponics?

Yes, commercially available fish emulsions for soil can also be used for hydroponics. It can be applied both as foliar spray and as a hydroponic water additive.

Are there ways to lessen the bad odor of fish emulsion?

Mixing essential oils such as lavender can decrease the unpleasant odor that fish emulsion produces. Aside from this, essential oils are also efficient in pest control as it hinders the growth of fungi and bacteria. However, you must remember that essential oils are used only in small amounts. Overusing them can result in plant death.

Summary of Fish Emulsion in Hydroponics

Fish emulsion is used in hydroponics because it is highly beneficial. It is an organic, mild, and nutrient-rich substance. Additionally, it promotes plant growth and reduces waste.

However, using fish emulsion in hydroponics also has drawbacks such as a high price, an unpleasant odor, the need for frequent reapplication, and it violates vegetarian/vegan principles.

Before buying fish emulsion, consider the production scale, economic value, and odor. To use this, dilute 1 tablespoon of fish emulsion in 1 gallon of water. This can be used on the leaves, as an additive to hydroponic water in large-scale gardens, or as the sole component of a hydroponic solution in small-scale gardens.


  • “Efficacy of organic amendments used in containerized plant production: Part 2 – Non-compost-based amendments” by Stewart-Wade, S.M. in Scientia Horticulturae
  • “Scale up your garden’s health with fish emulsion fertilizer” by Enroth, C. in University of Illinois Urbana‐Champaign
  • “Plant Growth Regulators: Their Use in Crop Production” by Harms, C.L. and Oplinger, E.S. in Iowa State University

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