Grow Beds and Media



Choosing correct Grow Media is about maximising the surface area for the nitrifying bacteria to colonise.


Things to consider:

Starting with a healthy system: Boiling and cleaning media before introducing it to your system.

Free and easy drainage to encourage air to the plant roots.

The pH of your media – to avoid nutrient lock out.

Introducing worms to your system (vermiponics)



Flood and drain / ebb and flow

Constant flow

Deep water culture (DWC)

Nutrient film techniques (NFT)



 Are just as they sound, they float on top of the water. They should be made of food grade materials, and are best for plants which require no root structure.

Celery – Swiss Chard – Beetroot – Radishes – Onions – Cauliflower – Leaf Lettuce – Arugula – Endive – Cress Collards – Mustard Greens Komatsuna – Spinach – Kale – Tatsoi

Grower’s Tip: FR may do best if floating bead filters are added to remove solids.

In hydroponics rafts are often made from styrene, however, because of the varied information on leaching, we recommend sourcing alternative food-safe closed-cell materials as an alternative option.


The grow media in the grow-bed is what many aquaponics systems use to aid the  biological/mechanical filtration. It can also provide a home for worms (vermiponics).

The growbed media needs to be the right size to allow oxygen to be drawn down into the growbed – under 8mm there is less air at the roots, and the small media may clog pipes. More than 16mm is harder for planting, and the surface area for beneficial bacteria is reduced. Although sometimes delicate seedlings benefit from being started in finer grow media such as coco coir plugs, which can be transplanted easily into your system.


Expanded clay pebbles

Are created by heating clay to high temperatures. This makes them more energy consuming and more pricey than gravel. However, clay pebbles are pH neutral so won’t affect water chemistry, although washing it is recommended to get rid of any excess dust, as a temporarily high pH cold occur otherwise.

Clay pebbles help control the temperature around the plant root and provide good surface area for the nitrifying bacteria to colonise.

Gravel or pea shingle

Is less expensive, but very heavy. Aquarium gravel is recommended, however if using builders gravel, you must consider where it is from, and make sure it has been thoroughly checked (for abrasive edges, shell and limestone) and washed. Much gravel, such as pea shingle contains shell and limestone, which increases the pH (alkalinity) of a system. Higher pH can cause ‘nutrient lockout’ whereby plants are unable to access some of their required nutrients.

You can use vinegar to test alkalinity of gravel/pea shingle: It’s simple to test for carbonates which would effect water pH; put a handful of the chosen media into a jar of white vinegar and give it a little stir or shake to dislodge air bubbles. If there are steady strings of bubbles rising from the substrate it’s because the acids in the vinegar are reacting with carbonates which would raise the pH of your water to make it alkaline. (Carbonates are sometimes used to deliberately raise or buffer pH)

Volcanic rock

This adds essential minerals and trace elements (Macro: Sodium, Phosphorous,  Potassium, Magnesium, Silicone, Chlorine, Sulphur and Calcium. Micro: Iron, Manganese, Zinc, Copper, Molybdenum, Selenium, Chromium, Cobalt, Boron) which encourage your plants to thrive.

It’s porous nature aids the filtration of the water. It is found in natural fish habitats as well as used in aquariums, however, there are different types of volcanic rock, such as pumice or red rock. Some are more suitable than others.

You can also use volcanic rocks in dust form to add to freestanding wormeries, as well as in regular gardening  to invigorate composting.

A few good foods to grow in these medias include:

Beans -Broccoli – Pak choi – Cucumber – Peppers – Chillies – Squash – Courgette – Tomatoes – Peas – Cilantro



Can be filled  with organic materials. Often the bed is fed water from the aquaponics system, but is not returned to the aquaponics system, so can be filled with soil, compost, and hay with sand/gravel beneath.

Used for root vegetables such as;

Beetroot – Onion – Sweet potato – Carrots – Potatoes – Radish – Turnip



Rope (more sustainable, but hemp rope is often sprayed with pesticides)

Perlite (non-renewable)

Coco coir (more sustainable, byproduct but has to travel far to reach UK)

Non-woven Mesh (not often organic)


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