Seaweeding Algae & Seaweed Growing

How Do I Grow Algae? 5 Step Guide to Home Seaweed Cultivation

how do i grow algae

If you’ve been wondering ‘How do I grow algae and seaweed at home’ and whether it’s even do-able, then this is for you. We explain how to create an edible seaweed growing set-up at home, that can be used for brown algae such as kelp.

For most of the Western world, the idea of eating seaweed and algae is a fairly new concept. But on the other side of the world, people have been consuming seaweed for centuries. In fact, if you have ever had the opportunity to try sushi, then chances are you have already consumed one of the most popular forms of kelp available on the market today. Even a wide variety of soups that are available from the supermarket, use seaweed as a form of seasoning.

However, most us of only have access to dried forms of seaweed and algae. The difference is like comparing dried or preserved vegetables with fresh ones, with the preserved forms being the inferior option. If eating fresh seaweed sounds appealing, one of the easiest ways to access it is to grow your own.

In this guide, we explain how you can grow your own edible and medicinal seaweed at home, using an aquarium and inexpensive equipment.

How Do I Grow Algae & Seaweed? Step-by-Step Guide

Although seaweed is generally harvested directly from the ocean, it is still possible to grow it at home. Since most of the world does not have access to seawater at home, you will need to make your own saltwater from scratch.

Depending on the particular type of seaweed that you choose to grow at home, the methods of growing can differ. Nevertheless, once you finally get the hang of growing seaweed at home, you’ll find that it is an excellent source of food, vitamins and nutrients to have on hand.

The most common type of seaweed to grow at home is kelp. As such, these seaweed growing instructions focus mainly on kelp and other algae with a similar growth habit. For specific types, refer to our articles on how to grow spirulina and how to grow sea moss.

What You Will Need:

Here are some of the most important tools you will need to successfully grow your own algae colony:

  • Large Aquarium
  • Aquarium Heater
  • Large Wide Rocks
  • Fresh Kelp
  • Sea Salt
  • Water
  • Aquarium Air Pump

Step 1: Gather Your Supplies

Start off by gathering all the supplies that you will need in order to set up your seaweed aquarium. Although you can use just about any size aquarium that you wish, the larger the aquarium, the easier it is to maintain the temperature and provide ample room for growth. After all, some species of kelp can grow several inches in a single day. You will also need an aquarium heater, and air pump, and other basic supplies.

Step 2: Set Up the Aquarium

Clean and rinse the aquarium well, and place it in location. The aquarium itself needs to be placed in a warm, sunny location. Kelp will require a large amount of sunlight every single day, and the water also needs to be warm enough for the kelp to flourish. By placing your aquarium in the sun, you can ensure that it will have plenty of light, and stay warm enough to ensure optimal growth levels. Since the kelp will need something to anchor to, start by placing your large flat rocks at the bottom of the aquarium, and install the air pump.

Step 3: Prepare the Water

Next, we need to start preparing the salt water for our colony.

Start by filling the aquarium with de-chlorinated fresh water until it is about two-thirds full.

Next, you’ll need to mix up the salt water. Depending on the size of the aquarium, this process may need to be repeated multiple times. To prepare the salt water:

  1. Heat a large pot of regular de-chlorinated tap water on the stove until it reaches 81°F (27°C).
  2. Once it has reached this temperature, add 1 tablespoon of sea salt for each gallon of water in the aquarium. For example, if your aquarium holds 20 gallons of water, you will need 20 Tablespoons (12.7oz) of sea salt in total.
  3. Let the salt completely dissolve in the water, then slowly pour it into the aquarium. Stir the water in the aquarium well.
  4. Once you’ve added all the salt water, top up the aquarium with fresh water until it is full.

Step 4: Adjust the Water Temperature

The optimal temperature for the seaweed’s growth is 72°F (22°C). You can buy cheap stick-on thermometers from pet shops to put on the side of the tank, to monitor water temperature.

If you live in a cooler location, then you will need to make use of an aquarium warmer in order to maintain this temperature consistently. If this is the case, install the aquarium heater, and bring it up to the right temperature.

If you live in a place that is warm and sunny year-round, this will be less of an issue. Instead, those living in warmer climates may have to deal with the issue of the water staying too warm for the kelp to survive. Using larger tanks in warmer climates helps to keep the temperature of the water cooler.

Step 5: Plant Your Seaweed

It’s important to obtain a stock of seaweed from a reputable location. Since most forms of kelp are often harvested near the shoreline, there is a greater potential for contaminants in the supply. This is why it is so important to research the company you are purchasing your stock from, to ensure that it is quality.

Like land-based plants, kelp has a root-like formation at the bottom. This mass is known as a holdfast, and it is the anchor the plant uses to attach itself to the rocks. As long as your seaweed is alive, it will usually grab a hold of the rock as soon it is placed in the water. However, if the rocks are too large, it will be difficult for the holdfast to grab a hold of them. Instead, you may need to move around smaller rocks to provide ample anchoring.

What does algae need to grow and survive?

Sunlight & Correct Temperature

In order to successfully grow algae at home, is important to create the most hospitable environment for the seaweed to flourish. This includes ensuring that the aquarium is placed in a location where it will get plenty of sunlight throughout the day. It’s equally important to ensure that the water itself is maintained at the optimal temperature.


Just like with plants, fertilizing plays an important role in ensuring optimal growth for algae. Commercial seaweed farms are located in the ocean, and they never need any form of fertilizer. However, because you are growing kelp at home, you will need to provide plenty of nutrients for the crop. Naturally, you will need to consistently fertilize the water over time with more nutrients to ensure that the kelp continues to survive and thrive.

Make sure that you are purchasing the proper fertilizer that has been specifically designed for algae. You do not want to use fertilizer for land-based plants on kelp. Make sure to follow the directions on the package when you are adding your fertilizer.


Out in the open ocean, there is a steady movement within the water. As waves break on the surface, the air is forced into the water. The currents and tide then pull that oxygen-rich water through the kelp forests. However, when you are growing seaweed in an aquarium, you have no current. Instead, you will need to make use of an aquarium air pump to oxygenate the water and provide agitation.

What types of seaweed I grow at home?

There are more than 3,500 different types of seaweed, that are broken down into 3 distinct groups. Brown and green seaweed are some of the most commonly found algae around the world. Red algae is also a very popular choice for the culinary arts. However, red algae also have one of the most complex reproductive systems of any algae group and are not generally recommended for home growers.

Brown Algae

Brown algae are the easiest of all seaweed to grow at home. In fact, common kelp is a form of brown algae. Growing brown algae at home is simple and straightforward, requiring very little experience and tools. While there are a number of other forms of brown algae that can be grown at home, virtually all of them can be grown in a similar manner to that of kelp.

Green Algae

Green algae are the second easiest seaweed to grow at home. However, due to its more complicated reproduction system, green algae require more experience to grow properly. See lettuce and see grapes are some of the most common forms of edible green algae.

Red Algae

Due to its more complex reproduction cycle, red algae is the most difficult to grow at home. Nori is the most common form of red algae used in the culinary arts. The method to grow red algae is a lot more complex than the instruction provided above. It’s always best to first get experience growing brown algae, before attempting to grow red algae at home.

Common Forms of Edible Seaweed

The following are the most common forms of edible seaweed used in the culinary arts.

Arame (Brown Algae)

Seaweed can be broken down into brown, green, and red types. One of the most common forms of brown seaweed consumed around the world is arame. This mildly flavored seaweed is very dark in color and is commonly sold in long strands that triple in size when placed in water. It is considered to be a very fiber-rich plant, that is also high in iodine. Compared to hijiki, it also has one of the mildest flavors in the brown seaweed group. Moreover, arame is considered to be one of the most versatile of all seaweeds. When kept in an airtight container, dried-out arame will last practically forever on the shelf.

Kelp (Brown Algae)

The largest of all the seaweed groups is kelp. Kelp can be found in every saltwater body in the world, growing in dense groups called kelp forests. It is located close to the shoreline and is known to have a meatier flavor than other forms of seaweed. As a result, it is a very common ingredient for use in soup stocks. Like many other seaweeds, it also is high in iodine, which makes it great for thyroid gland regulation. It is important to remember that due to its high iodine content, it should not be consumed too often. Nevertheless, when thoroughly dried out and stored in an airtight container, kelp will last virtually indefinitely on the shelf.

Nori (Red Algae)

When it comes to seaweed wraps, nothing beats nori. Also known as purple laver, this purplish black seaweed is composed of more than 30% protein. It has a high level of beta-carotene, niacin, and folic acid, as well as vitamins a and C. It has a very pleasant flavor and is perfect for spicing up your next plate of rice or pasta. It is also an excellent garnish for fish and can be used for miso soup as well as vegetable salads. Unlike other forms of kelp, when thoroughly dried and stored in an airtight container, nori will generally only last up to 3 years. If the seaweed turns a yellowish color, then it should not be consumed as it may already have gone bad. As a red algae, it is more difficult to grow than the instructions provided here.

Final Thoughts on “How Do I Grow Algae & Seaweed?”

We hope that by the end of this article, you have now gained a good understanding of how to grow your own edible seaweed at home. If you’ve ever kept pet fish in an aquarium at home, you probably have most of the skills (and possibly the tools) already. Growing seaweed and algae is not much different from caring for aquarium fish. They have similar needs, such as a constant, suitable temperature, oxygen and food (nutrients).

If you are still wondering ‘how do I grow algae and seaweed at home’, here’s a quick recap of our 5 steps:

  1. Gather your supplies. This includes aquarium, air pump and heater, plus algae and nutrients.
  2. Set-up the aquarium. This includes choosing a suitable location, and installing the pump and rocks.
  3. Prepare the water. This includes filling the tank, and mixing the salt water.
  4. Adjust the water temperature. Do this by choosing the right location, and/or using a water heater.
  5. Plant your seaweed. Finally, place your seaweed into the tank.

That’s it. Observe the tank to ensure that it keeps looking healthy, and fertilize as needed. Similar to how you feed pet fish using special fish food, likewise you feed algae using specifically formulated nutrients. Pick up some pre-mixed nutrients for salt-water based water plants, and follow the label. Aside from that, clean your tank every now and again to keep the system fresh and healthy, and have fun.

Happy seaweeding!