How to grow SEA MOSS at home - Seaweeding Algae & Seaweed Growing (2023)

Interested in growing your own aquatic sea moss (aka irish moss) at home? We explain how to grow sea moss at home step-by-step, and how to sustainably harvest irish moss from the wild.

Sea moss has grown in popularity over the past couple of years. As more and more people turn to algae as a form of superfood, they have begun seeking out the easiest forms to grow at home. And although a lot of people today have heard of spirulina and other forms of seaweed and algae, the popularity of sea moss has been limited to northern Europe.

This spiny little sea plant is generally found along the rocky shorelines of North America and Europe. It has the same general appearance as Spanish moss which can be found in trees throughout the southern United States, only it grows entirely underwater.

Where Does Sea Moss Grow?

There are two main options when it comes to the commercial propagation of sea moss: wildcraft and grown. In other words, it can either be farmed or it can be harvested in the wild. Let’s take a deeper look at these two variations.

Wildcrafted Sea Moss

Wildcraft sea moss specifically refers to algae that are planted and harvested in the wild. That is, farms are created offshore in an ideal growing location, where the growth of the sea moss is monitored from time to time. Eventually, the algae are harvested and brought ashore to dry.

When compared to pool grown sea moss, wildcraft sea moss is generally known to have a higher density of nutrients. The reason for this is that wildcraft sea moss receives a steady supply of nutrients from the flow and ebb of the tide. When the algae are grown in a pool, the amount of nutrients they receive is limited by the grower.

Unfortunately, as a result of wildcrafting, sea moss has become threatened naturally. Wildcraft sea moss has a lot more nutrients than other forms. It is also a lot harder for farmers to collect. A farmer would need to spend excessive amounts of time in a diving suit, collecting the sea moss from the ocean floor. Although still available in some areas of the world, more and more commercial establishments are opting for pool-grown and ocean-farmed setups instead.

Pool Grown Sea Moss (Farmed)

Most of the sea moss available today has been grown on a farm. Pools are used by farmers because they are sustainable and controllable. Simply put, while it is easier to grow sea moss in the ocean, the harvesting of algae from a growing pool does not threaten the species, and the grower has the ability to control the optimal growing environment.

Sea moss that is grown in a pool, has a lower nutrient content when compared to that which is grown at sea. At the same time, it is also more gelatinous in nature. Some people even refer to the pool grown sea moss as a fake form, which can be easily identified through its lighter color.

For those choosing to grow sea moss at home, even when starting with wildcraft algae, the final outcome will be a paler, less vibrant color. Nevertheless, pool-grown sea moss provides ample amounts of vitamins and nutrients.

When grown in pools, farmers do their best to replicate not only the temperatures and salinity of the ocean but also attempt to replicate the movement of the tides as well. While this may not always be possible, depending on location and setup, the sea moss will grow nonetheless.

Ocean Farmed

Some farmers even choose to set up an ocean-based farm. This type of farm is similar to a pool system but relies on the natural ebb and flow of the tides and currents. The farms are set up off the shore, and generally feature a deck that surrounds the farm, with ropes and other equipment to raise and lower the sea moss in and out of the water.

Farmers place strong ropes underwater in order to entice the sea moss to grab hold. Farmers generally will dive into the water, and locate their ropes, in order to begin harvesting the sea moss. This process is generally repeated two times every single month during the blooming season.

Next, we’ll explain how you can grow your own sea moss at home using an aquarium, which is essentially a small-scale pool grown sea moss set-up.

How to Grow Sea Moss at Home

Step 1: Gather Your Supplies

Unlike other forms of algae, sea moss can be grown in both freshwaters as well as saltwater. However, it is always best to grow in saltwater.

In order to grow sea moss at home, you will need the following supplies:

  • 20 Gallon Aquarium and Air Pump
  • Natural Sea Salt
  • Nutrients and Minerals
  • Wildcrafted Sea Moss (Chondrus crispus)

20 Gallon Aquarium

For growing sea moss at home, it is best to start with a 20-gallon aquarium. This should be more than enough, to grow enough algae for several people. You can use a standard fish tank, that you can find at any local pet store. You may also opt for any large UV-resistant clear tote, depending on the amount of sun and the average temperature in your area.


As with most forms of algae, it is important to supply your farm with enough nutrients. The most common nutrients needed for the successful propagation of sea moss, include:

  • Ammonium Sulfate
  • Calcium Chloride
  • Citric Acid
  • Iron Sulfate
  • Magnesium Sulfate
  • Potassium Nitrate
  • Salt
  • Sodium Bicarbonate

This nutrient mix is basically the same as that for growing spirulina. Some stores specializing in aquatic plants, such as Aquatic Live Food sell pre-mixed nutrient mixes for marine algae.

Wildcrafted Sea Moss

Make sure that when selecting your initial algae, you choose something that has been harvested from the ocean. This will ensure that your sea moss does not contain any harsh or dangerous chemicals that could otherwise affect your health or the plant’s growth. If you live near the ocean and have access to wild sea moss, then harvest it yourself during the next bloom. It is important that the algae you start with is still alive when you put it in the water.

Although there are a number of different forms of sea moss that can be grown in pools, it’s very important that you are only purchasing and consuming Chondrus crispus. When purchasing your initial plants, make sure to avoid pool-grown sea moss as much as possible, and ensure that the company specifies that it has been wildcrafted or ocean farmed. This ensures that the algae have not grown in a pool with any unknown dangerous chemicals.

Step 2: Prepare the Tank

Next, set-up your aquarium and air pump. Make sure you clean your equipment very well with natural cleaners (don’t use chemical cleaners, unless they are specified for aquarium use), to avoid any cross-contamination.

In order to get the best growing experience possible, you will need to place your tank out in the sun. Not only will this ensure that your mini-farm gets plenty of sunlight, but it will also ensure that the water stays warm enough to provide an optimal growing environment.

Although the sea moss does not necessarily require any rocks or sand, you may use some river rocks or sand at the bottom of your tank. This will provide something for the algae to grab a hold of once it starts to grow.

Step 3: Prepare the Water

Although it is possible to grow sea moss in freshwater, it is best to create the proper saltwater environment or it to thrive. To do this, mix 1 tablespoon of natural sea salt with 1 gallon of warm fresh water. A standard 20-gallon tank will require 20 tablespoons of sea salt.


  • 1 US Tablespoon Sea Salt (18g / 0.6oz) to 1 Gallon Water (3.8L)
  • 10 US Tablespoons Sea Salt (180g / 6.4oz) to 10 Gallons Water (38L)
  • 20 US Tablespoons Sea Salt (360g / 12.7oz) to 20 Gallons Water (76L)

Step 4: Add the Sea Moss

Once you have filled the tank with salt water, you can then place your wildcraft sea moss into the bottom. Unlike other forms of algae and seaweed, it may not grab a hold of the rocks right away. Simply check back from time to time and make sure that the water stays agitated. To help with water agitation and oxygenation, it is best to also use an aquarium air pump. This will create a more realistic, and natural environment for the algae.

Step 5: Add Nutrients

From time to time you may need to add additional nutrients to the water. You can find nutrients for growing seaweed online, or at a wide variety of health-food stores across the country. It is important to use a nutrient mix that is specifically designed for algae, rather than using standard plant-based fertilizer, as this will ensure the best and safest results.

Unfortunately, it is not well documented how often to fertilize home-grown sea moss. However, if we follow spirulina growing as an example, it is suggested to add one tablespoon nutrient every time it is harvested. Some sources suggest that aquatic mosses need less nutrient than other algae, however, so it is probably best to err on the side of caution and use less rather than more.

We’ll update on this once we receive more information on the ideal frequency and quantity of nutrient required on a regular basis for sea moss to thrive. Feel free to write to us if you know the answer. For the meantime, we suggest you follow the instructions on the nutrient you purchased.

How to Harvest Wildcrafted Sea Moss

If growing sea moss if not your thing and you live in an area where sea moss is known to grow, you may simply harvest it at low tide. When the tide goes out, you will find the sea moss hanging from the side of rocks, or even floating in tide pools. This is where most growers and divers get their wildcraft sea moss from.

Below are some pointers for collecting sea moss from the wild. Before you head out, however, we recommend you speak to someone who knows the local environment, to ensure that you know how to identify sea moss correctly and are not inadvertently collecting some other algae.

Keep a Sustainable Mindset

Before you harvest anything from the wild, including seaweed, make sure you do it in a sustainable manner. Never collect too much from one area to allow the colony to continue to flourish, and only collect as little as you need at one time. Pay attention to and respect local regulations, as some jurisdictions may not allow harvesting wild plants and algae.

The Right Timing

It is also important to make sure to time the harvesting just right. There is a lot of planning necessary to ensure that wildcraft sea moss is harvested at the peak of its bloom. This ensures that the best samples can be harvested from the water.

Watch the Tides

Tides also play an important role in the harvesting season. It is always best to harvest the sea moss when the tide is low. Most wildcraft farmers make use of a tidal chart on a regular basis. They take time to plan their harvesting trips around the lowest tide of the cycle. This ensures the greatest amount of algae can be harvested sustainably with the least amount of effort.

Use a Sharp Knife

Since the sea moss grabs a hold of the rocky shores, you will need to make sure to bring a sharp knife with you. There may be some excellent pieces of moss that are firmly attached to the rocks, which will need to be cut off.

Use Plastic Bags

From there, you will need to use plastic bags in order to collect everything that you find. The more you plan on collecting, naturally, the larger the bags you will need. Just make sure that the bags will keep the sea moss moist until you are ready to process it.

Final Thoughts on How to Grow Sea Moss

That’s it! Continue monitoring your sea moss colony, and fertilize as required. For maintenance, follow the instructions on the nutrient you purchased. Form time to time, like with any aquarium set-up, it is a good idea to re-fill it with new water and give the tank a good clean, to avoid any cross-contamination with unwanted algae and bacteria.

For further reading, we suggest you read this guideline from the FAO on algae production, although its scientific and commercial focus may be too technical for most home growers. At this point in time, there are unfortunately very few resources on growing aquatic sea moss at home, which means you may be limited to scientific and industry publications. For specific questions, have a talk to your local aquarium supply store for personal advice. We’ll continue to update this post as we acquire more information about optimum home sea moss growing conditions.

Happy seaweeding!


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