Choosing the correct mineral amendment determines whether the substrate drains, retains moisture, controls pests, or provides nutrients for years. Gardese's seven amendments cover complementary functions: three expanded minerals for drainage and aeration (perlite, vermiculite, expanded clay), two volcanic materials for heavy drainage and decoration (volcanic gravel, pumice), and two active minerals for specific treatments (zeolite, diatomaceous earth). This comparison helps you decide which fits your substrate or operation.
🎯 Choose in 10 seconds
- If you need maximum drainage and aeration in professional substrates: go to Expanded Perlite
- If you want to retain moisture and nutrients in seedbeds: go to Expanded Vermiculite
- If you work with hydroponics or want lightness with superior drainage: go to Expanded Clay Pebbles (Arlita)
- If you decorate with mineral mulch and improve drainage in pots: go to Volcanic Gravel
- If you grow cacti, succulents, or hydroponics with a stable volcanic substrate: go to Pumice
- If you filter pool water, retain fertilizer, or control ammonia: go to Zeolite
- If you control crawling pests without chemicals and provide silicon: go to Diatomaceous Earth
What to consider before choosing
Before buying a mineral amendment, evaluate these four criteria. They define whether the substrate will fulfill its agronomic function or become compacted and lose performance.
- Main function of the substrate: fast drainage (perlite, expanded clay), water retention (vermiculite), heavy structural drainage (pumice, volcanic gravel), filtration or ion exchange (zeolite), or physical pest control (diatomaceous earth). Each function requires different material.
- Appropriate particle size for the crop: seedbeds and propagation work with fine particle sizes (1-3 mm); substrates for mature pots with medium sizes (3-6 mm); drainage layers and decorative mulch with coarse sizes (6-20 mm). Mixing incorrect sizes results in uneven drainage or root asphyxiation.
- Structural stability over time: perlite and vermiculite compact with frequent watering and lose function in 1-2 years. Pumice, volcanic gravel, and expanded clay are ceramic or volcanic materials that maintain structure for years, a decisive advantage in professional potting or permanent substrates.
- Compatibility with organic production: zeolite and diatomaceous earth are approved by certified organic farming standards. If your operation has an organic audit, verify that the material you will use as a substitute for conventional fertilizer or pesticide has the corresponding endorsement.
Expanded Perlite: universal drainage and aeration
- Fine (1-3 mm) and medium (3-6 mm) particle sizes in 100 L bag
- Neutral pH, chemically inert, does not alter mixes
- Sterile material free of pests and seeds
- Expanded volcanic glass with calibrated porosity
- Fine dust when handled dry
- Tends to float on the surface after several abundant waterings
Expanded perlite in a 100 L (26.4 gal) bag in fine or medium particle size. Mixed at 20-40% with a base substrate, it improves aeration, prevents waterlogging, and prevents root rot. Compatible with any formulation: black soil, coco fiber, peat moss, and professional hydroponic mixes.
Expanded Vermiculite: moisture retention for seedbeds
- Fine (1-3 mm) and medium (3-6 mm) particle sizes in 100 L bag
- Lamellar structure that absorbs water and releases it slowly
- Mineral sterility for commercial seedling production
- Neutral pH compatible with any mix
- Does not provide fast drainage like perlite
- Higher unit cost than other basic amendments
Expanded vermiculite in a 100 L (26.4 gal) bag in fine or medium particle size. The fine acts as a seedbed cover for uniform germination; the medium in mixes for cuttings and plants requiring constant moisture. Modern expanded mineral without the historical contamination of old industrial batches.
Expanded Clay Pebbles (Arlita): hydroponics and permanent drainage
- Particle size 8-16 mm in 40 L bag
- High-temperature ceramic without decomposition
- Superior drainage with modulated retention due to internal porosity
- Suitable for lightweight concrete and thermal insulation
- Large size not suitable for seedbeds or fine mixes
- Higher cost than perlite and vermiculite
Expanded clay pebbles (Arlita) in a 40 L (10.6 gal) bag in 8-16 mm particle size. Ceramic balls are the standard medium for hydroponics with recirculating systems, NFT, and aquaponics: inert, washable, and indefinitely reusable. They also work as a drainage base in large pots, decorative cover, and aggregate for lightweight concrete.
Volcanic Gravel: heavy drainage and decorative mulch
- Extra-coarse particle size 10-20 mm in 25 kg bag
- Available in red and black for aesthetic integration
- Thermal insulation for root zone in Caribbean climate
- Sterile, does not harbor pests or attract termites
- Large size not suitable for fine substrate mixes
- Permanent red or black color with no modification option
Volcanic gravel in a 25 kg (55 lb) bag in extra-coarse 10-20 mm particle size, in red or black. The porous volcanic rock absorbs water and releases it gradually, reducing watering. Ideal as decorative mulch over soil, a drainage layer at the bottom of planters, and a base substrate for cactus and succulent collections in xeriscaping.
Pumice (Pumice Stone): stable drainage that does not float
- Fine (1-3 mm) and medium (3-6 mm) particle sizes in 40 L bag
- Stable structural density: does not float like perlite
- Neutral pH, chemically inert
- Bioavailable silicon contribution to the crop
- Higher unit cost than perlite
- Limited availability to fine and medium particle sizes
Pumice (pumice stone) in a 40 L (10.6 gal) bag in fine or medium particle size. The calibrated volcanic stone maintains a stable position in the substrate for years, a decisive advantage over perlite which floats to the surface after several waterings. Ideal in substrates for cacti and succulents (up to 50% of the mix), improvement of clay soils, and lightweight concrete aggregate.
Zeolite: filtration and ionic retention
- Four particle sizes (extra-fine 0.5-1 mm to coarse 6-9 mm) in 25 kg bag
- High cation exchange capacity (releases nutrients gradually)
- Retains particles up to 5 microns (superior filtration to silica sand)
- Approved in certified organic production
- Does not function as a primary drainage improver
- Higher cost than conventional silica sand for filters
Zeolite (clinoptilolite) in a 25 kg (55 lb) bag in four particle sizes. Extra-fine and fine are used in agricultural substrates for nutrient retention; medium in pool and aquarium filters; coarse in draining beds with an ion exchange function. Captures ammonia, chloramines, and heavy metals without added chemicals.
Diatomaceous Earth: physical pest control
- Natural uncalcined, micronized diatomaceous earth, in 20 kg bag
- Physical insecticidal action by contact without generating resistance
- Bioavailable silicon contribution strengthens cell walls
- Compatible with certified organic production
- Not a primary drainage or water retention amendment
- Dry application: loses effectiveness with excessive moisture
Diatomaceous earth in a 20 kg (44 lb) bag in natural micronized presentation. The fossilized silica acts as a physical insecticide against ants, cockroaches, fleas, aphids, and crawling pests: it perforates the insect's cuticle and dehydrates it without chemical compounds against which resistance develops. It also works as an absorbent for spills and moisture control in stables.
Comparative table
| Characteristic | Perlite | Vermiculite | Expanded Clay | Volcanic Gravel | Pumice | Zeolite | Diatomaceous Earth |
|---|---|---|---|---|---|---|---|
| Main function | Drainage and aeration | Water retention | Hydroponic drainage | Drainage + decoration | Stable drainage | Filtration / exchange | Pest control |
| Granulometries | 1-3 / 3-6 mm | 1-3 / 3-6 mm | 8-16 mm | 10-20 mm | 1-3 / 3-6 mm | 0.5-1 to 6-9 mm | Micronized |
| Presentation | 100 L bag | 100 L bag | 40 L bag | 25 kg bag | 40 L bag | 25 kg bag | 20 kg bag |
| Color | White | Light brown | Brown | Red or black | Beige | Light beige | White |
| Structural stability | Medium | Medium | High (years) | High (years) | High (years) | High (years) | — |
| Suitable for organic production | Yes | Yes | Yes | Yes | Yes | Yes — admitted | Yes — admitted |
| Use in construction | Yes (lightweight concrete) | — | Yes (lightweight concrete) | Yes (pozzolan) | Yes (lightweight concrete) | Yes (pozzolanic) | — |
Use case matrix → recommended product
| If your case is… | Recommended product |
|---|---|
| Mix professional substrate with good drainage | → Perlite |
| Make seedbeds with uniform humidity | → Vermiculite |
| Hydroponics with recirculation system | → Expanded Clay |
| Decorative cover and mulch in the garden | → Volcanic scoria |
| Grow cacti or succulents with stable drainage | → Pumice |
| Filter pool water replacing silica sand | → Zeolite |
| Control ants and crawling pests without chemicals | → Diatomite |
| Retain fertilizer in crops with fertigation | → Zeolite |
| Improve compacted clay soils | → Pumice |
| Propagate cuttings with constant humidity | → Vermiculite |
Before buying the amendment, define two pieces of information: the dominant function (drainage, retention, decoration, filtration, or pest control) and the granulometry according to the crop (fine for seedbeds, medium for mature pots, coarse for drainage and mulch). Combining amendments often yields better results than a single one: for example, perlite + vermiculite 50/50 for universal substrate, or pumice + expanded clay in hydroponics with recirculation.
Do not use diatomite as an insecticide in permanently moist soil or with frequent irrigation. The abrasive action of fossilized silica depends on keeping the material dry; as soon as it gets wet, it loses its ability to pierce the insect's cuticle and becomes ineffective. Apply it to a dry surface in thin layers and reapply after rain or heavy watering.
What amendment does your substrate need?
If you work with a specific substrate, hydroponics, commercial seedbeds, or organic farming with auditing, the correct material can be a single amendment or a calibrated mixture. Ask the virtual assistant with details of the crop, system, and agronomic objective for an instant technical recommendation.
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Frequently Asked Questions
Can I mix several amendments in the same substrate?
Yes, and in fact, it is common professional practice. The most used mixtures are perlite + vermiculite 50/50 for universal potting soil, perlite + black earth + coco fiber 30/40/30 for vegetables, and pumice + expanded clay 50/50 for hydroponics with recirculation. Each amendment provides a different function, and combining them balances drainage, retention, and structure.
What is the difference between perlite and pumice if both provide drainage?
Perlite is expanded light volcanic glass that tends to float on the surface after several abundant waterings and slowly compacts. Pumice is pumice stone with stable structural density that maintains its position for years without floating. For temporary pots or seedbeds, use perlite; for permanent substrates for cacti, succulents, or hydroponics with prolonged use, use pumice.
Does zeolite replace chemical fertilizer in crops?
It does not replace it, but it does amplify its performance. Zeolite acts as a reservoir for ions (potassium, calcium, magnesium, ammonium) which it retains from applied fertilizer and gradually releases according to plant demand, reducing leaching from watering and waste. In practice, the grower continues to apply fertilizer but in smaller doses and with improved uniformity.