How each medium affects the system
Aeroponic (no medium, misted roots)
Also known as: Aeroponics, High-pressure aeroponics, Low-pressure aeroponics
- Highest possible root oxygenation: roots hang in humid air and are intermittently misted, with the plants spending almost all of their time in air, which supports very fast growth when run correctly
- Pump failure or clogged nozzles kill plants within minutes to hours, since there is no buffer reservoir or medium moisture
- Calibration-sensitive: fine hydro-atomized droplets of roughly 5-50 microns are used for true high-pressure aeroponics, and performance falls off outside that range
- Difficult retrofit: most hobbyist aeroponic setups are purpose-built tower or chamber systems rather than adaptations of other hydroponic methods
Currently not a supported system in the garden planner, since it sits outside the dwc/nft/vertical/drip/media-bed/wicking/soil-bed enum. It is listed here as reference material, and future planner work may add aeroponic as a system option. It is realistic for advanced hobbyists with a high-pressure pump, accumulator tank and timer-controlled solenoids. NASA has funded aeroponics research, partly for controlled-environment and space-agriculture applications.
Suitable systems: aeroponic.
Avoid in: media-bed, nft, dwc, drip, wicking, soil-bed.
Expanded clay pebbles
Also known as: LECA, Hydroton, Clay balls, Expanded clay aggregate, ECA
- Excellent biofiltration substrate for aquaponics: the highly porous surface (total porosity up to about 80%) is colonized by nitrifying bacteria, reducing or eliminating the need for a separate biofilter
- Light enough that a 4x8 ft media bed stays movable when dry
- Inert and pH-neutral (around pH 7): it does not buffer pH, so system pH drifts toward the source water's natural value
- Floats when first added dry, so pre-soak for about 24 hours before stocking plants or it will displace water from the bed
- Cheap-grade product releases clay dust on the first fill; rinse aggressively until the water runs clear
A standard hydroponics and aquaponics workhorse medium for any system where pebbles suit. It is reusable for years; rinse between crops to clear root debris, and sterilize between sick-plant cycles with a bleach soak (1:9 bleach to water) followed by a triple rinse and re-pH. The pellets are fired in rotary kilns at around 1,200 C, which expands the clay like popcorn into light, porous, roughly round aggregate that resists compaction.
Suitable systems: media-bed, drip, wicking.
Avoid in: nft, dwc.
Coco coir
Also known as: Coconut coir, Coco peat, Cocopeat
- Natural pH is mildly acidic, roughly 5.5-6.8, usually within crop targets without adjustment
- Coir pith is naturally high in potassium (and often sodium), which can induce calcium and magnesium deficiencies in soilless media, so a CalMag supplement is commonly needed
- Cheap unbuffered coir is salt-laden from processing; buy buffered/washed grade or soak it in a calcium-buffering (CalMag) solution and leach before use
- Breaks down over 2-3 cycles, eventually compacting and losing drainage
Frequently mixed with perlite (50/50 or 70/30) for hydroponic Dutch-bucket systems to add drainage. Pure coir works well for hand-watered or drip-irrigated Dutch buckets. Buy buffered coir (RHP-certified) or pre-rinse and calcium-buffer cheap coir before planting, since coir pith is naturally rich in potassium and sodium and can otherwise lock up calcium and magnesium.
Suitable systems: drip, dutch-bucket, wicking, soil-bed.
Avoid in: nft, dwc, media-bed.
Lava rock
Also known as: Scoria, Volcanic rock
- Best-in-class biofilter substrate: extremely porous, more bacterial surface area per liter than clay pebbles
- Heavy: a 4x8ft media bed of lava rock weighs significantly more than clay pebbles when wet; build the stand accordingly
- Sharp edges: handle with gloves; can damage soft roots of seedlings on initial transplant
- Cheap source for biofilter media if available locally; check vinegar test (no fizzing = inert)
Source matters: red and black scoria from landscape suppliers is fine, but some agricultural lava products are dust-heavy and need rinsing. The sharp edges that can scrape soft roots also lock plants in place once rooted, which helps tall fruiting crops that would otherwise need staking. A simple vinegar test (no fizzing means no carbonate and an inert rock) confirms suitability.
Suitable systems: media-bed.
Avoid in: nft, dwc, drip, wicking.
Net pot, no medium
Also known as: Bare-root, Net cup, Net pot with no growing medium
- Roots dangle directly in oxygenated nutrient solution (DWC) or sit in a shallow recirculating nutrient film (NFT); a growing medium plays no role
- Plant support is purely mechanical: the net pot collar holds the stem while the bulk of the root mass develops below the pot
- Pump or air-supply failure can kill plants quickly, since bare roots have no medium reservoir; DWC relies on an airstone and air pump, while NFT's recirculating film self-oxygenates
- Easiest cleanup between cycles: rinse the net pots and reuse them indefinitely
The simplest approach for DWC and NFT. Plants are usually started in a small rockwool or coco-fibre starter plug, then moved into a net pot once roots emerge from the bottom of the plug; after transplant the plug stays as a tiny support cube while the bulk of the root system grows bare in solution. In DWC the net pots sit in a floating raft with roots submerged and oxygenated by an airstone, and in NFT they sit above a shallow recirculating nutrient film.
Suitable systems: dwc, nft.
Avoid in: media-bed, drip, wicking, soil-bed.
Pea gravel
Also known as: Pea stone, River gravel, Aquarium gravel (smooth varieties)
- pH depends entirely on stone composition: limestone-based gravel raises pH (vinegar test fizzes), silica/quartz/basalt gravel is inert
- Vinegar test BEFORE filling a system: drop white vinegar on a few stones; bubbling means calcium carbonate is present and the gravel will buffer pH upward
- Very heavy: a 4x8ft gravel media bed needs a solid stand and may need reinforced flooring
- Smooth surface compared to lava or clay pebbles: less bacterial colonization, biofilter capacity is moderate not high
Often the cheapest viable media-bed substrate in a given region. Always test for inertness before committing a system to it: a few drops of white vinegar (a weak acid) that make the stones fizz reveal calcium carbonate, which will buffer system pH upward, while silica, quartz or basalt gravel stays inert. Some commercial aquaponics farms use crushed basalt or river gravel for the cost advantage, accepting the lower biofilter performance.
Suitable systems: media-bed.
Avoid in: nft, dwc, drip, wicking.
Perlite
Also known as: Expanded volcanic glass
- Almost always used in a mix, not pure: pure perlite holds no water and dries out too fast for most crops
- pH neutral and inert; does not buffer or affect water chemistry
- Smooth glass surface: poor bacterial colonization compared to porous media
- Compacts and degrades over time, eventually creates fines that clog drip emitters
Wet perlite before adding it to a system, or you will breathe the dust; wear a silica-filtering mask when handling it dry, since perlite is largely silicon dioxide. It is a standard component of coir-perlite hydroponic mixes and is rarely used alone except in some Dutch-bucket setups for fast-draining crops like strawberries.
Suitable systems: drip, dutch-bucket, wicking.
Avoid in: nft, dwc, media-bed.
Pumice
Also known as: Volcanic pumice, Horticultural pumice
- Lighter than lava rock with similar bacterial surface area: a good compromise medium for media beds where weight matters
- Less sharp than lava rock; safer for handling and on soft roots
- Regional availability: widely sold in volcanic regions (Pacific Northwest, Italy, Japan, New Zealand), harder to source elsewhere
- Mixed sizes available: smaller grades work for drip systems, larger for media beds
Underused medium that fills a niche between clay pebbles (expensive, manufactured) and lava rock (heavy, sharp). Where available locally, often cheaper than clay pebbles with better biofilter performance.
Suitable systems: media-bed, drip, dutch-bucket.
Avoid in: nft, dwc.
Rockwool
Also known as: Mineral wool, Stonewool, Grodan
- Manufactured pH around 7.0-7.8; must be pre-soaked in pH 5.5 water (mild nutrient solution) for 24 hours before sowing
- Sterile by nature: no microbial buffering, so beginner-friendly but unsuited to aquaponics which needs the biology
- Compresses over time as roots fill the cube; one-shot transplant medium
- Holds excess water near stem base: risk of damping-off in seedlings, root rot in mature plants if oversaturated
Handle with gloves and a dust mask. Standard commercial-hydroponics starter cube. Most starts from seed begin in a small 1.5-inch rockwool cube, then transplant into a larger system. Not recommended for aquaponics: the biology that defines aquaponics has nothing to colonize on sterile mineral fiber.
Suitable systems: nft, dwc, drip, flood-and-drain.
Avoid in: media-bed, wicking, soil-bed.
Soil-based mix
Also known as: Potting soil, Garden soil, Compost-amended mix, Container mix
- Brings its own biology: any aquaponics or hydroponics system that uses soil ceases to be aquaponics or hydroponics in the strict sense
- pH depends on the base: peat-based mixes are naturally acidic and are usually limed with chalk or dolomite to a working pH around 5.5-6.5, while compost-heavy mixes run neutral to slightly alkaline
- Holds nutrients between waterings, reducing the frequency and precision of nutrient management compared with soilless systems
- Pest and pathogen vector: introducing field soil into a clean indoor setup is a common route for fungus gnats (which lay eggs in moist soil) and root-knot nematodes, which is why commercial potting soil is usually sterilized
Used in wicking-bed systems and traditional in-ground or raised-bed gardens. The site lists soil-bed as a system option because many readers grow some crops in soil alongside their hydroponics/aquaponics setup, and the garden planner skips chemistry rules in soil-bed mode. Most modern potting mixes are largely soilless, built on peat, coir or bark with perlite or vermiculite for aeration.
Suitable systems: soil-bed, wicking.
Avoid in: nft, dwc, media-bed, drip, dutch-bucket.
Vermiculite
Also known as: Expanded mica
- Holds 3-4 times its weight in water: excellent for seed germination and seedling propagation, dangerous for mature plant roots which can drown
- Almost always mixed with perlite for active growing (perlite provides air, vermiculite provides water reserve)
- Compresses heavily over time; one or two crop cycles before replacement
- Has cation-exchange capacity; can mask early Mg/Ca deficiency similar to coco coir
Primarily used for seed-starting in plug trays rather than as the active growing medium of a hydroponics system. Vermiculite is an exfoliated mica (a hydrated phyllosilicate) that puffs into light, accordion-shaped granules when heated. Modern horticultural vermiculite is tested and sold asbestos-free, but older bulk product (pre-1990, from the Libby, Montana mine) was contaminated with amphibole asbestos, so buy horticultural-grade from a reputable supplier.
Suitable systems: wicking, soil-bed.
Avoid in: nft, dwc, media-bed, drip.