Seaweed Fertilizer Vs Fish Fertilizer | Which Is Best?

When it comes to your garden and landscaping, fertilizer is one of the best ways to ensure beautiful produce, healthy growth, and lush blooms. However, with so many different kinds of fertilizers on the market, it’s hard to know which is best.

Fish and seaweed fertilizers are attractive options because they are more natural alternatives to fertilizers that use harmful chemicals. Although they may seem very similar, fish and seaweed fertilizers are distinct, and each has unique benefits and drawbacks.

Here is everything you need to know about seaweed fertilizer vs fish fertilizer.

Difference Between Seaweed vs Fish Fertilizer

There are several significant differences between these two types of fertilizers. What they’re made of, what they’re best for, and how they can be used will differ and can impact your choice.

Seaweed Fertilizer

Firstly, seaweed fertilizer is, as the name suggests, made out of seaweed. The majority of this is kelp, which is very rich in nutrients and minerals. Just as seaweed has proven to be an excellent superfood for humans, it also contains types of materials not found in other kinds of plants that benefit health and growth.

These unique nutrients have several other special benefits, such as activating a natural and slow-release mechanism within the soil. This extends the benefits of the fertilizer over time as it works to improve both the plants and the soil.

Seaweed fertilizer also helps increase the water absorbency of the soil and the solubility of the minerals and nutrients within the ground.

And, of course, it’s safe and nontoxic. Like many natural fertilizers, the downsides of seaweed fertilizer include the need to dilute it before use, its higher price point, and its sometimes fishy smell.

Fish Fertilizer

Fish fertilizer is unique because it’s made with the whole fish carcass, including the skin, scales, and bones. These components add essential nutrients and nitrogen content to the end mixture, which is called a fish emulsion.

When applied to the soil, fish fertilizer increases the amount of natural, organic matter by interacting with the soil’s ecosystem, including worms, fungi, and microbes. 

Calcium is a unique component of fish fertilizer that often isn’t present in chemical fertilizers. Calcium enhances the soil and helps protect plants of all kinds against diseases, bulking their natural defenses to make them heartier.

N-P-K Ratio

All fertilizers have a ratio of nitrogen, phosphorus, and potassium, which are all key ingredients that must be balanced to feed the soil adequately.

Fish Fertilizer N-P-K

On average, fish fertilizer has an N-P-K ratio of around 4-1-1 or sometimes even 5-1-1. Hence, it’s high in nitrogen because of the high organic material, but it’s low in phosphorus and potassium.

For this reason, fish fertilizers are loved for providing nitrogen-specific benefits when they’re needed in the soil. Nitrogen is the component that plants need most to grow and produce healthy crops, so many gardeners apply nitrogen-rich fertilizers to prepare the ground right before the growing season.

Seaweed Fertilizer N-P-K

Liquid seaweed fertilizer is unique in that its N-P-K ratio is, on average, 0-0-1, meaning that it offers potassium and other vital minerals and nutrients to the soil but lacks nitrogen and phosphorus.

This doesn’t mean that seaweed fertilizer isn’t beneficial to plants and the soil. On the contrary, it offers natural and sustainable benefits that many other fertilizers don’t. However, it shouldn’t be the only additive used to nourish your plants and balance the soil.

How to Use Fish and Seaweed Fertilizer

Because of their more natural composition, both fish and seaweed fertilizer can be applied in both traditional and nontraditional ways to help your plants benefit fully.

Foliar Spray Application

One unique way to apply both these natural fertilizers is through foliar feeding. Because plants also take in nutrients through their leaves, natural fertilizers can be applied topically through a spray once every two to three weeks.

This is an excellent option for newly sprouted or transplanted plants slowly acclimating to their new soil environment. 

In situations where plants have difficulty absorbing nutrients through their roots, like high soil pH, cold weather, or excess soil moisture, topical absorption can help make them more resistant to frost.

It can also be applied during the plant’s flowering to help increase its production yield.

Of course, a plant’s main avenue for nutrient absorption is through the roots, so foliar feeding is supplementary at best and often a temporary solution.

Soil & Root Application

Store-bought fish and seaweed fertilizers can come in many forms, often in powdered or condensed emulsion forms. Both need to be diluted with water according to instructions before applying to soil.

Usually, the blend will be a small amount of concentrated fertilizer to a more considerable amount of water that can be applied directly onto the soil with a standard watering can

Soil and root application are especially beneficial because fish and seaweed fertilizer act to improve the soil and help it release natural nutrients, starting a cycle of nourishment and growth that continues throughout the season.

Can You Over-Fertilize?

In many cases, seaweed or fish fertilizer can be applied as often as you water your plants. For many gardens during the spring and summer, this can be as often as twice a week. 

However, with fish fertilizer specifically, it’s important to pay attention to the nitrogen concentration in your soil. As fish fertilizer is particularly high in nitrogen, overusing it can overload your soil with this compound that can burn plants’ roots in too great a concentration.

Is Seaweed Fertilizer vs Fish Fertilizer Better? Final Thoughts

Each of these unique, natural fertilizer options can bring beneficial properties to your soil as well enhance the growth potential of your fruit and vegetable crops, trees, and shrubs. Choose a fish fertilizer if your soil needs a boost of nutrients and added nitrogen and apply it before the growing season starts.

Choose seaweed fertilizer for application during the growing season as it will enable the soil to provide valuable minerals and nutrients thus increasing yield and bountiful growth as well as helping to reduce the risk of disease, reduce stress, and boost overall plant health.

Of course, some fertilizer brands combine the powers of both seaweed and fish fertilizer into one product and my particular recommendation for a great combination fertilizer is Down To Earth Bio-Fish.

It has an N-P-K of 7-7-2 to not only ensure that your soil receives an all-natural source of nitrogen but also to encourage healthy foliage, as well as voluminous blooms and fruit.

Down To Earth Bio-Fish 7-7-2