Block of compressed coco coir removed from its packaging, dense brown fibre block on a white background

Rehydrated coco coir held in both hands, airy texture blending peat, fibres and chips

UGro XL Rhiza 70 L compacted coco fibre block, full packaging seen from a three-quarter angle on a white background

UGro Slab Rhiza 15 L grow bag, one-metre-long coco coir block, on a white background

UGro implementation diagram for the 15 L bag: cutting the windows, hydrating, making drainage slits, placing the plugs

Compressed coco fibre brick seen at three-quarter angle on a white background

UGro Slab Rhiza 15 L coco coir block in its one-metre white packaging, placed diagonally on a white background

Hydrated coco coir expanded view – swollen coco substrate for aquaponic grow bed

UGro compressed coco coir, 15 L bag or 70 L block

$9.72

Volume	Price	Price per L	vs 15 L
15 L	$9.72	$0.65	—
70 L	$21.26	$0.30	−54 %

UGro Rhiza coir, washed twice in fresh water and buffered at the factory, comes out at pH 5.5 to 6.5. It is available in two formats, which are not prepared in the same way.

The 15 L growing bag is planted as it is after receiving 6.5 L of water, whereas the 70 L block, rehydrated with 18 L of water, fills your own pots and baskets.

Growing medium

Volume : 15 l

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The summary

What you receive: washed, buffered UGro Rhiza coco coir, in a 15 L grow bag or a 70 L block.
How long it takes: 20 to 30 minutes of expansion for the 70 L block, a good hour of resting for the 15 L bag.
Preparation: 6.5 L of clean water for the 15 L size, 18 L for the 70 L size, and a container for the final volume.
Before commissioning: a rinse with clear water, and that water must not be returned to the fish tank.
What maintenance is needed: none for the grow medium, only watering or fertigation of your crops.
How to choose: the 15 L bag is planted as it comes, the 70 L block fills your own pots.

Washed and buffered coco fibre, in a grow bag or as a block to rehydrate

UGro Rhiza compressed coco fibre serves as a planting medium in pots and baskets, thanks to its pH of 5.5 to 6.5 after a double rinse in fresh water. The 15 L grow bag can be planted as it is after adding 6.5 L of water, whereas the 70 L block, rehydrated with 18 L, fills your own containers.

Once compressed, coco fibre fits on a shelf: the 15-litre grow bag weighs just 1.6 kg before it is watered. It regains its volume the day you moisten it, so you can store a dense format all year round and make up the grow medium when you need it, without cluttering a garden shed over the winter. Both formats share the same fibre, washed twice in fresh water and buffered at the factory, but they are not prepared in the same way.

The 15 L bag

It is a flexible grow bag of about one metre, UV-treated, which you place and plant as it is.

The 70 L block

It is a block to rehydrate in a container, to fill your own pots and baskets.

💧 Preparing a block

Preparation requires no tools. The 70-litre block needs 18 litres of clean water and expands in 20 to 30 minutes in a large tub or wheelbarrow. The 15-litre bag is prepared differently: you cut open one of the four marked positions on top, pour 6.5 litres of clean water through that opening, then let capillary action distribute the moisture before planting. Allow a good hour for the bag to become evenly moist along its whole length.

🌿 Coir in aquaponics

In aquaponics, coco fibre serves as a planting medium, in pots and baskets. It holds the root ball, keeps moisture around the roots and offers a surface that bacteria colonise. Keep it for that use rather than filling a whole flood bed with it, where its fineness ends up packing down the medium and reducing circulation. The guide on which grow medium to choose in aquaponics compares the options one by one.

Rinse the fibre and measure out the rehydration water

The start-up rinse must not be skipped, because in aquaponics it prevents the first leaching water from being sent to the fish tank. So run the rehydrated grow medium under clean water and drain that water elsewhere. Soaking the block excessively is of no use either, since beyond the quantities indicated the fibre loses volume and compacts instead of staying airy. Finally, keep it out of the bottom of a flood bed, where its fineness makes it migrate towards the strainer and the pump.

A complete fertiliser from the very first watering

Coconut fibre supplies almost no nutrients, so everything depends on what you add: in hydroponics on coconut fibre, a complete fertiliser feeds your plants from the very first watering. If you are filling your own pots and baskets, the 70-litre block is the one to choose, since the 15-litre bag is planted as it is, through the marked openings on top.

♻️ After the crop

Used coco fibre does not necessarily have to be thrown away. After a healthy crop, it can be shaken out to remove the roots, rinsed thoroughly and used a second time, with slightly reduced water retention and a somewhat finer structure. After a root attack, however, it goes to the compost heap rather than into the next pot, because a fibrous grow medium holds on to spores far better than a mineral medium. Compost remains its natural end of life, since it breaks down slowly there while improving the structure of heavy soil.

Technical specifications

The essentials

Volume once hydrated: 15 or 70 litresDepending on the capacity chosen.
Rehydration water: 6.5 or 18 litresDo not exceed this: beyond it, the fibre compacts instead of staying airy.
Grow medium pH: 5.5 to 6.5The range in which most vegetables absorb minerals best.
EC conductivity: Below 0.6 mS/cmOn new grow medium, before any fertiliser is added.
Water retention: 40 to 65 % depending on size40 to 45% for the 15 L bag, 60 to 65% for the 70 L block.
Reuse: A second season in potsRemove the large roots and rewet the material, provided the previous crop had no root disease.

To budget for separately

Water and container: 6.5 or 18 L of clean waterPlus a washing-up bowl, a wheelbarrow or a tub large enough for the final volume.
Fertilisation: A complete fertiliserAll the nutrition comes from what you add, from the very first watering.

In the box

1 grow bag of 15 litres of hydrated medium, with 4 marked planting positions to cut out, drainage holes underneath and a UV-treated film (15 L variant)
1 compressed block of 70 litres once hydrated, 32 x 32 x 14 cm, in film with a carrying handle (70 L variant)

Hydrated volume, rehydration water, pH, conductivity, retention and weight: values stated for this product, taken on 10/09/2026. Retention and structure differ from one format to another; details are given beneath each line.

15 litres or 70 litres: which one is right for you

Both sizes contain the same washed and buffered coco fibre, but they are not prepared in the same way and do not serve the same purpose.

The same fibre, two ways of setting it up The bag is planted up as it is, with nothing to transfer. The block is expanded in a washing-up bowl and fills your own pots, all at once or in several batches.

	Volume once hydrated (L)	Clean water to have ready (L)	Weight of the parcel to carry (kg)	Packaging	Fibre structure	Water retention	Enriched with endomycorrhizae	Prepared in several stages	Ready to plant without transferring	Fills your own pots and baskets	Price	Best value for volume
15 L grow bagYour choice	15 L	6,5 L	1,6 kg	Flexible bag, marked spots to cut out	Medium grade, long fibres and chips	40 to 45%	Yes	No	Yes	No	$9.72	No
Recommended 70 L compressed blockYour choice	70 L	18 L	5 kg	Shrink-wrapped block, 32 x 32 x 14 cm	Medium grade, medium share of fibres	60 to 65%	Yes	Yes	No	Yes	$21.26	Yes

15 L grow bag

Format and rehydration

Volume once hydrated (L)15 L

Clean water to have ready (L)6,5 L

Weight of the parcel to carry (kg)1,6 kg

PackagingFlexible bag, marked spots to cut out

How the grow medium behaves

Fibre structureMedium grade, long fibres and chips

Water retention40 to 45%

Enriched with endomycorrhizaeYes

Prepared in several stagesNo

In use

Ready to plant without transferringYes

Fills your own pots and basketsNo

Price$9.72

Best value for volumeNo

70 L compressed blockRecommended

Format and rehydration

Volume once hydrated (L)70 L

Clean water to have ready (L)18 L

Weight of the parcel to carry (kg)5 kg

PackagingShrink-wrapped block, 32 x 32 x 14 cm

How the grow medium behaves

Fibre structureMedium grade, medium share of fibres

Water retention60 to 65%

Enriched with endomycorrhizaeYes

Prepared in several stagesYes

In use

Ready to plant without transferringNo

Fills your own pots and basketsYes

Price$21.26

Best value for volumeYes

Technical values taken from the Slab Professional Rhiza and XL Rhiza datasheets.

Product videos

A UGro XL 70 L block expanding in real time

Rehydrating a coco fibre block, step by step

Growing in coco coir: the basics

Preparing and planting a UGro grow medium, demo on the Small format

Growing in coco bags explained

Documents & manuals

Catalogue UGro Coco, Tree of Life 2024

Full range of UGro coco grow media and the characteristics of each product. English and Spanish.

PDF · 4,4 Mo

Download

UGro 2022 range leaflet

Detailed compositions of the Slab 15 L and XL 70 L, weights and volumes. English and Spanish.

PDF · 2,9 Mo

Download

UGro product catalogue

Condensed datasheets for the full range, dimensions and pack sizes. English and Spanish.

PDF · 3,3 Mo

Download

Rhiza 1200 instructions, the mycorrhizal inoculant

Manufacturer's document on endomycorrhizae in the Rhiza range. In English.

PDF · 2,2 Mo

Download

Estimate your
delivery time

The 70-litre block weighs 5 kg, and the 15-litre one about 1.6 kg. The exact delivery cost is calculated at the basket according to the total weight of your order.

Frequently asked questions

6 questions

6 key questions

Which capacity should you choose, 15 or 70 litres?

Format	Water to add	Set-up	Who it suits
15 L grow bag	6.5 L	Plant straight into it: cut out the marked planting spots on the top.	A growing table, a gutter or a workstation already in place.
70 L compressed block	18 L	Expand it in a container, then spread it across your own pots and baskets, all at once or in several batches.	Those who already have their own containers, plenty of space and don't mind a little handling.

Per litre of hydrated medium, the 70 L block works out noticeably cheaper than the 15 L bag. The comparison of the two formats settles it in three questions.

Coco fibre or clay pebbles: which should you choose for soilless growing?

These are two opposite functions, often complementary rather than competing.

Clay pebbles drain. Clay pebbles shed water very quickly and retain almost none: they are made for flood-and-drain beds with short cycles, where the grow medium must empty completely at each cycle, and for bottom drainage.

Coco fibre retains. It holds water between waterings, with a capacity of 40 to 45% for the 15 L bag and 60 to 65% for the 70 L block. It is therefore suited to pots, planters, seedlings and any plants that cope poorly with swings in moisture.

Sphagnum and perlite play different roles. Sphagnum retains considerably more water and keeps its structure for a long time, but it is expensive per litre and is used mainly for cuttings, orchids and carnivorous plants. Perlite is not a complete grow medium: it is added to coco fibre to lighten it. Potting compost, for its part, supplies nutrients that you do not control, which is a drawback in soilless growing.

For a full overview, see the article on choosing a grow medium in aquaponics and the collection of growing media.

How much water is needed to rehydrate a coco coir block?

6.5 Lfor the 15 L bag

18 Lfor the 70 L block

20 to 30 minfor the block to expand

Do not exceed these quantities. The bag is filled with clean water through one of the cut-out openings on top, then you leave it to rest while capillary action spreads the moisture; the block expands in a large washing-up bowl.

Adding more water does not give you more grow medium: the material becomes saturated, loses volume and compacts, which harms rooting.

One side of the 15 L bag will look wetter than the other at first: this is normal, as the capillary action of the fibre spreads the water by itself.

Should coco coir be rinsed before it is used in aquaponics?

This fibre can be planted once hydrated, with no other preparation. In aquaponics, still carry out a commissioning rinse, because otherwise the water from the first leaching runs off towards your fish tank.

Rehydrate the block with the specified amount of water, 6.5 L for the 15 L bag, 18 L for the 70 L block.
Break up the material by hand or with a hand cultivator.
Run it under clear water until the water runs clear.
Dispose of this first water in the garden or down the drain, never into the fish tank.

This fibre is already washed twice and buffered at the factory, with a conductivity below 0.6 mS/cm. But coir keeps a high exchange capacity: in contact with soft, nutrient-poor water, it releases some of the potassium and sodium still bound to it.

Does coco fibre lower the pH of the water?

How should an unused block of coco coir be stored?

Compressed and dry, in a frost-free place, it keeps from one season to the next without any problem: ambient humidity is its only enemy. Compressed, the 70 L block fits into 32 x 32 x 14 cm, roughly 5 times smaller than its volume once hydrated.

Once rehydrated, the grow medium should be used straight away; if any is left over, keep it damp and aerated rather than sealed in an airtight bag.

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UGro compressed coco coir, 15 L bag or 70 L block

The summary