How to Prepare Coco Coir Bricks to Grow Microgreens

We love to use coconut coir as the main ingredient of our microgreen growing media.

We currently use bags of loose coir, but we would like to purchase coco coir bricks as it would be more economical and take up less storage room.

For the home microgreen grower, using coco coir bricks would also be ideal in theory. But for every positive aspect, there can also be a negative factor to take into account and find a solution to make it work.

In this article, we will go over the pros & cons of coco coir bricks. We will also explain the following.

  • Show how to expand the coco coir bricks in a video;
  • Determine how much water to use to expand a brick;
  • Provide ideas on how to store the extra coir;
  • Measure how much loose coir is in a coco coir brick; and
  • Discuss how well pure coco coir grows microgreens.
coconut coir as microgreen soil

Coco Coir Bricks - What Are They?

If you are unfamiliar with coconut coir, what it is, where it comes from, how it is processed, its advantages, and the renewable & sustainable properties; in that case, we have published an in-depth article that has become very popular

Therefore, we won't touch on those topics. Instead, we will concentrate on managing coco coir bricks and how much loose coir is contained in a brick.

But first, the pros and cons of coco coir bricks.

Coco Coir Bricks Pros vs. Cons

Our thoughts on coconut coir bricks and their usage (in no particular order).

Pros:

  • Compact size takes up little room .
  • Brick is a convenient shape - easy to stack and store.
  • Reduces shipping cost both for seller and buyer.
  • Tightly sealed & dry - much less chance of fungus gnat infestation. 

Cons:

  • Needs preparation before use. 
  • Once expanded excess moisture can cause mold issues in leftover coir.
  • Pure coconut coir needs additives for best plant growth.
  • We don't recommend throughly wet soil when planting microgreens. Coir from bricks is completely wet.
  • We have wasted coco coir from bricks because of improper handling. 

We will discuss each of these in more detail later in the article. But first, let's expand a brick of coconut coir! 

Below is a video of a coco coir brick expanding. The data collected is presented below and manipulated to assess other sized bricks for your use.

We go deep into the numbers later in the article to figure out the best way to buy coconut coir.

I had intentions of fast-forwarding through much of this, but I brought up some good points throughout the video. 

I was surprised by how this coco coir brick expanded. I expected more from it, like the coco coir puck shown in my Instagram video.

As you saw in the Instagram video (@myviewfromthewoods), I just poured water into the nursery pot indiscriminately.

That's because the pot has holes in the bottom, and any excess water will drain out. Also, I was planting tomato sets, and extra moisture isn't a problem.

Why Moisture Is A Problem With Coco Coir Bricks

If you're using all of the coconut coir from a brick, moisture isn't a problem. However, in most cases, when planting microgreens, you only need a small amount of coir compared to how much a brick will expand into (more on this later).

So the extra coconut coir will need to be stored, and if it holds too much water, mold will quickly grow on the coir. 

You can, of course, leave the top off the container and allow the water to evaporate and the coir to dry out. 

However, what can happen is that fungus gnats will be attracted to the moist soil and lay eggs. From then on, all Hell breaks out.

Where do fungus gnats come from anyway? I'll have to research that. 

So adding enough water to the brick without over-saturating the coconut coir is the trick we need to learn.

Coconut Coir Moisture Content Is Deceiving

As you saw in the video, coconut coir has the uncanny ability to look perfectly moist, but in reality, it's saturated.

Even the fluffy coconut coir in the video not only dripped water, but it flowed out in a steady stream. 

This is too wet to plant microgreen seeds on, especially those susceptible to damping off disease, such as beets and Swiss chard, or those that take more than a couple days to germinate. 

Coco Coir Bricks By The Numbers

Before we get to recommendations, let's go over the numbers and make a couple of assumptions.

First, the facts.

Dimensions and Expansion

The Coco Bliss coco coir brick dimensions in the video are 8- by 4- by 2-inches.

what is coco coir brick

That makes the volume of the compressed brick 64 square inches. 

Once the coco coir brick was expanded, the volume was measured to be 476 square inches.

That is 8.25 quarts for those familiar with the 8-quart bags sold by garden centers. 

Therefore the coco coir brick expanded 7.4 times its size.

Can We Assume That All Bricks Are Compressed The Same?

No, I don't think we can. 

Here's why.

1.4-Pound Brick

Our compressed brick of coir was 64 square inches. It weighed 1.45 pounds.

We will calculate how many square inches are in a pound of compressed coconut coir to normalize the bricks.

64 divided by 1.4 is 45.7 cubic inches per pound. 

10 Pound Brick

According to Amazon, the 10 pound Coco Bliss (same brand) coir brick is 12 by 12 by 5.5 inches. That is 792 cubic inches.

792 divided by 10 is 79.2 cubic inches per pound.

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The Smaller Brick is Much More Dense

The smaller 1.4-pound coco coir brick is 1.7 times as dense as the 10-pound brick. That is the same as saying pound for pound the smaller brick has 1.7 times more coir. 

I'm not going to compare all of the brands, but you can compare how much coir you will get out of any coconut coir brick from the example above.

How Much Coconut Coir in a 10 Pound Brick

Assuming that a particle of coir is the same weight once expanded. We can consider this correct; we can estimate how many quarts of expanded coir we can get from a 10 pound Coco Bliss 10 pound brick.

The inverse of 1.7 is 0.59. So, from the 1.4-pound brick, we can calculate that we will get 340 cubic inches of coir for each pound of compress coir.

Since the 10-pound brick is 0.59 times less dense, we should get 200.6 cubic inches for each pound.

So a 10-pound brick would yield 2,006 cubic inches or 34.7 quarts which is 1.2 cubic feet.

Most bagged loose soil is sold in 1.5 or 2 cubic feet bags. 

From these numbers, we can make cost comparisons to soil media products in stores. 

We can also determine if it's wiser to buy more small bricks or larger bricks. 

How Much Water is Needed to Expand a Coco Coir Brick?

The value we recommend below is a value we've been searching for for a long time.

Most videos or articles say to add water and dump in a random amount.

Maybe they plan on using all of the coir?

I don't know. 

What I do know is that I have thrown quite a bit of coconut coir into the compost heap because it was stored too wet, and mold grew on it. 

Remember, we want to expand the coir to the moisture level to store it without having mold grow on it.

Seems like a simple problem to solve, but as the video showed you, coconut coir is really good at storing water and not looking wet. 

We use about two-thirds of a gallon of water (about 2.4-liters) with the 1.4-pound brick. 

Sorry to switch between units here, but for liquid measure, liters are easier, and all measuring cups also have liter measurements on them. 

As mentioned in the video, 2.4-liters was too much water. 

Even trying to be careful, I overdid it. 

Doing it again, I would start with 2-liters of water and, if necessary, allow the coir to sit awhile and absorb the water slowly as not to over-wet the coir. 

Can We Use The Recommend 1.4-pound Value on Other Bricks? Truthfully, I'm not sure.

If I tried to expand the 10-pound brick referenced above, I would normalize the water amount to a pound of coir and multiply by the density difference. 

The normalized value would be 2-liter (2,000-mL) divided by 1.4 or about 1,430-mL per pound.

Since the 10-pound brick is 0.57 times as dense, I'd use 815-mL per pound of coir. So for the 10-pound brick, I'd start with 8-liters of water and see how it goes. 

Using Other Brands of Coco Coir Bricks

You should be able to use my numbers with other brands of coco coir bricks. Find their density and compare it to the 1.4-pound Coco Bliss brick and go from there. 

Storing Expanded Coco Coir

As mentioned, I've thrown out quite a bit of coir when I was messing around with hydroponics.

I'd mix it in a 5-gallon pail, use what I needed and store the rest with a tight lid. The next time I went to use some, sure enough what remained in the bucket was covered in mold.

This is why I'm so concerned with finding the perfect amount of water!

Instead of pails, I now store soil in totes. Either the HDX brand or Rubbermaid brand.

The tops seal tight enough to keep insects out, but they do breathe some and allow air exchange. 

Over wet or saturated coco coir will still mold if you're not careful.

How Wet is Too Wet?

If you grab a small handful of coconut coir and squeeze it, water should not drip out of the coir. 

Your hand may have moisture on it, but if any water drips out of the soil, you shouldn't cover it tightly. 

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The Coir in the Video - How to Dry Out Wet Coir

I did over wet the coir in the video. Water was dripping out even after quite a bit of mixing.

To dry it out, I placed the container in front of a fan (not so close the coir flew out) and let some of the water evaporate.

When the top dried out and was light brown, I mixed it up again to let the dry coir absorb some of the wetness and bring some of the moisture up to let the fan dry it. 

What I have now is a beautiful container of coco coir that smells like earth and not mold. 

How Well Does Coir Grow Microgreens?

Honestly, not well.

At least not pure coir.

Below are links to a couple of articles that show how well microgreens germinate in coir but then stall out.

The Best Soil For Microgreens

Which Soil Is Best For Slow-growing Microgreens?

However, with additives, there is nothing better, according to my tests.

I have run dozens of trials, most of them documented on this website.

These show that with the correct additives, coco coir outperforms peat moss based potting mixes and for sure any fiber mat.

One of the purposes of expanding the coco coir brick is to use the result to test organic liquid fertilizers and vermicompost in pure coir to see how well microgreens grow. 

We don't give up trying to find the best combination to grow microgreens. We present the tests, and you can make up your own mind on how you want to grow microgreens. 

Home Microgreens is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. As an Amazon Associate, we earn from qualifying purchases. We may earn a small commission from the companies mentioned in this post at no additional cost to you. Not all links are connected to affiliate companies.

Are Coco Coir Bricks a Value?

I think this question is premature. 

As it is, pure coir will not grow the best microgreens. So although we can provide a price comparison without the additives' cost, it's a moot point.

But as mentioned, we will show those results in future articles and add those costs to the ones shown below. You will have a better idea of the cost differences.

1.4-pound & 10-pound Coco Coir Brick Cost

It used to be that you could choose to purchase 1.4-pound coco coir blocks in any quantity from 2 to 50. But know they sell them in 5-packs.

I recommend the Coco Bliss brand because it's certified organic and one of the larger companies. We hope that their quality control is top-notch.

Coco Bliss now also offers 250-gram bricks (~1/2-pound). These might even be better for home microgreen growers. 

The density of the 250-gram brick is between that of the 1.4- and 10-pound bricks -- about 30% less coconut coir per pound, or 5.8 quarts per pound. So a 250-gram brick should produce about 3.2 quarts of expanded coconut coir.

You can see the current price from Amazon below.

Strange, but at the time of publishing, Coco Bliss is only offering a minimum of 20 1.4-pound bricks. Hopefully that changes.

Cost Per Quart Coconut Coir

Using the prices at the time of publishing this article, let's calculate the cost per quart of expanded coconut coir. From this, you can compare the costs with your favorite microgreen soil.

  • 250-gram brick is $2.40
  • 1.4-pound brick is $4.00
  • 10-pound brick is $35

We will consider the density difference of the bricks and assume that this will normalize the expansion.

250-gram Brick of Coco Coir*

A brick should expand to 3.2-quarts, so a quart will cost about 75-cents.

*but you have to buy 10...

1.4-pound Brick of Coco Coir*

A brick does expand to 8.25-quarts, so a quart will cost 48-cents.

*but you have buy 20...hopefully they will offer less bricks.

10-pound Brick of Coco Coir

A brick should expand to 34.7-quarts, so a quart will cost $1.01.

Coco Coir Brick Takeaways

Here are some points to consider when deciding if you want to use and expand coco coir bricks to grow microgreens.

With Coco Coir Bricks Density Matters

Always check the density of the coco coir bricks when you are comparing the cost.  The product listing should contain the size of the bricks.

Density is equal to the volume (length x width x height) / weight.

What Brand to Buy?

We have always used Coco Bliss bricks and have found them to be consistent and always clean. 

Other brands might be as good, but we have no experience with them. Below are the top sellers on Amazon.

If you've used any of these or another brand, leave a comment below and let us know how you liked the product.

Use Limited Water

Expand the bricks slowly, adding a little water at a time. Over wet coconut coir will not store well and, in most cases, will grow mold.

Even if you plan on using all of the coir, don't oversoak the coir as it retains a lot of water and may impact seed germination.

Saves on Shipping Costs

Coconut coir bricks will save you money on shipping. Remember, even free shipping is free. It's built into the cost. The compressed nature of the bricks makes them much more ideal for shipping than loose soil.

You Need More Than Coir to Grow Plants

Coconut coir will germinate plants well, but it needs additives (granular or liquid) to grow good plants. 

It is basically nutrient deficient. 

See this article.

Calculating How Much Water to Use

For a brick with a density of 0.022 pounds/ cubic inch, we recommend 1.4 liters of water per pound of compressed coir.

To estimate how much you should use for other blocks, find your brick's density and divide it by 0.022. Then multiple that value by 1.4 to find out how many liters of water you need to add per pound of your brick.

More Articles on Using Coir with Additives

This post's actual purpose is to set up a series of articles using a variety of additives and fertilizers with pure coco coir to see how well it performs.

Of course, we will be comparing how the additives do our own Home Microgreens potting mix and pure coir. 

You should look for these kinds of tests. Many growers show you microgreens, and they look great. Still, it is tough to judge without comparing it to a known top performer and a control tray.

We will link the articles here once they have been published.

Click the button below, and we'll email you when a new article is published.

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Author of this Article is Todd

Todd is the founder of Home Microgreens & the Home Microgreens store. He also writes for several other websites, including MakeGardeningEasy.com. Todd worked at a large farm market, garden & nursery center for 20-years. Somehow he snuck off to become a geologist and professor before coming back to his senses to write & lecture about microgreens and gardening. When not at the computer, he can be found in the garden, trout stream, or mountain trail with his new Springer Spaniel Caden.

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