DIY Pon Recipe: Mineral Ratios, Particle Sizing & Preparation

What Makes a Good DIY Pon?

Pon is a mineral substrate designed so that roughly half of its pore volume holds water and half stays filled with air. Commercial Pon is a blend of zeolite, pumice and lava rock, and you can reproduce it from bulk minerals at a lower cost per liter and with more control over what goes in. The recipe below is a community standard for hobby growers, and all ratios are by volume, measured with one scoop or container for all three minerals. For how the finished substrate behaves in a pot, including capillary rise and reservoir depth, read the semi-hydroponics with Pon guide.

The Golden Mineral Ratio: 3 : 2 : 1

The base mix is 3 parts pumice, 2 parts zeolite and 1 part lava rock by volume, which is about 50%, 33% and 17%.

• 3 parts pumice (50%). Pumice is a lightweight volcanic glass full of internal pores. It supplies the structural macropores that stay filled with air, holds a moderate amount of water and is close to chemically neutral.
• 2 parts zeolite (33%). The useful zeolite for plants is clinoptilolite. It has a high cation exchange capacity (CEC), so it captures positively charged ions such as ammonium and potassium (and, to a lesser degree, magnesium and calcium) and releases them gradually. This buffers the swings between feeding and flushing. Zeolite also tends to stabilize the root-zone pH in a roughly neutral range, around 6.5-7.0 in many setups, but the exact pH depends on your water and product, so test it with a meter if you grow pH-sensitive plants.
• 1 part lava rock (17%). Basalt or scoria adds weight so tall plants do not tip, gives roots something to anchor to and releases small amounts of iron, magnesium and other trace elements.

To work out volumes for any pot or batch, use the semi-hydro Pon calculator. The batch table above covers common sizes.

Particle Sizing and Grading

The target grain size is 3-6 mm (1/8 to 1/4 inch). Particles in this range leave enough gaps between grains to stay air-filled, while the pores inside the grains hold water.

Why Fines Must Be Screened Out

Anything under about 2 mm behaves like sand or silt. These fines sift down between the larger grains, fill the macropores and hold water by capillary tension, so the root zone ends up wet, dense and short of oxygen. That is the opposite of what Pon is meant to do, and it is a leading cause of root rot in homemade mixes. Screening is not optional, even when the bag says it is graded.

How to Screen

1. Stack two sieves or screens: a 6 mm mesh on top (hardware cloth of 1/4 inch works) and a 2-3 mm mesh below (a kitchen colander with small holes or window screen over a frame).
2. Shake the mineral over the top sieve. Material that stays on top is oversize and can be crushed and re-screened, or used in the bottom layer of tall pots.
3. Material that stays on the lower sieve is your target grade.
4. Material that passes through the lower sieve is fines. Discard it or use it in garden soil.

Screen dry, outdoors or over a tarp, because mineral dust is irritating to breathe. Wear a dust mask, since fine pumice and zeolite dust contains respirable particles, and wet the minerals slightly if dust is a problem.

Washing and Dust Removal

Even screened minerals carry a coating of fine dust that sticks to roots and clogs pores once wet. Wash each mineral separately before mixing.

1. Put a few liters of mineral in a bucket or in a mesh bag or sieve set inside a bucket.
2. Fill with water, stir vigorously by hand or with a paddle, and pour off the cloudy water, keeping the minerals back.
3. Repeat until the water runs completely clear. Pumice and zeolite usually need 4-8 rinses.
4. Drain and spread the washed minerals to dry slightly, or mix them damp, then blend the three components thoroughly.

Do not pour the muddy rinse water down a household drain in large quantities, because mineral silt can settle in the pipes. Use a garden bed or a catch bucket.

Sourcing Each Mineral

• Pumice. Choose pumice sold for horticulture, bonsai or aquaria in a 3-6 mm grade. Landscape pumice is often a mix of sizes with many fines.
• Zeolite. Buy pure clinoptilolite sold for gardening, aquaria or soil amendment. See the cat litter warning below.
• Lava rock. Use undyed, untreated volcanic rock such as basalt or scoria. Avoid dyed, sealed or painted decorative rock. Large chunks need crushing and screening.

Cat Litter Zeolite: Read the Label Carefully

Some cat litters are made of zeolite, but many are not suitable. Avoid any litter that is clumping (usually sodium bentonite, which swells into a gel and seals the pores), scented or deodorized (fragrance and chemical additives), or contains silica gel crystals or antimicrobial additives. Only use a product that lists 100% clinoptilolite zeolite with no additives, and rinse it thoroughly. When in doubt, buy zeolite sold for plants or aquariums.

Fertilizer Integration

Pon holds some nutrients on the zeolite, but it does not feed plants by itself. You can supply nutrients in one of two ways.

Option 1: Unfertilized Mix with Liquid Feed

Leave the mix plain and feed through the reservoir with a dilute liquid fertilizer, following the schedule in the semi-hydro fertilizer dosing guide. This gives the most control, and it is the safer option for cuttings, seedlings and salt-sensitive plants.

Option 2: Controlled-Release Fertilizer in the Mix

Resin-coated pellets such as Osmocote or Nutricote (the 6-9 month types) release nutrients slowly as water moves through the coating. A common rate is 2-3 grams per liter of mineral substrate, blended evenly through the mix, which is about 0.5-0.75 teaspoon per liter. Weigh it if you can, because pellets vary in size and density. Always check the product label, since formulations and recommended rates differ.

• Mix the pellets evenly through the whole batch rather than layering them at the bottom, where they would sit in the reservoir water.
• Release speed depends on temperature. The labelled 6-9 months applies at about 21 °C (70 °F). Warm rooms release faster and cool rooms slower.
• Empty shells may show up in the Pon as the nutrients are used up. This is normal.
• Flush the Pon monthly with lukewarm water to remove accumulated salts, as described in the Pon guide.
• You can still add a weak liquid feed during peak growth, but reduce it when using controlled-release pellets to avoid overdosing.

Mixing the Batch Step by Step

1. Screen each mineral to 3-6 mm and discard the fines.
2. Wash each mineral until the water runs clear.
3. Measure by volume using one container: 3 scoops of pumice, 2 of zeolite, 1 of lava rock.
4. Blend in a large tub or on a tarp until the colors and sizes are evenly distributed.
5. Add fertilizer if you are using controlled-release pellets, at 2-3 g per liter of finished mix, and blend again.
6. Soak the finished mix in plain water for several hours or overnight, drain and use it damp. This hydrates the pores and removes any dust left over.

Use the finished Pon in the pot systems described in the Pon guide, and see the guide to converting houseplants to semi-hydro for planting steps. Large aroids such as Monstera deliciosa are a good first plant for a homemade mix.

Substitutes and Adjustments

• Perlite instead of pumice. Not recommended. Perlite is lighter, crushes easily, floats to the surface and breaks down into fines over time. Pumice is far more stable.
• LECA or calcined clay. These can replace part of the pumice, but they are more water-retentive or can break down. For a comparison of materials, see LECA vs Pon.
• No lava rock. You can skip it and use a 3:2 pumice-to-zeolite mix, but you lose some weight and trace elements. Use heavier containers for tall plants.
• More pumice for orchids and Hoya. Plants that dislike wetness benefit from a ratio nearer 4:2:1 or from adding bark-free coarse pumice.
• More zeolite for hungry plants. Heavily fed plants can use a 3:3:1 ratio, though a higher zeolite share holds more water.

Reusing Screened Minerals

All three minerals are inorganic and reusable. After a plant is removed, shake out roots and debris, rinse until clear, and sterilize by boiling for about 10 minutes or soaking in diluted 3% hydrogen peroxide. Re-screen the minerals, since grains break down gradually and produce new fines. Zeolite holds fertilizer ions, so flush reused mix thoroughly before replanting to avoid carry-over salts.

Troubleshooting Summary

Related Resources

Learn how the finished mix behaves in the semi-hydroponics with Pon guide, move plants over with the conversion guide, compare materials in LECA vs Pon, set a feeding plan with the fertilizer dosing guide, calculate quantities with the semi-hydro Pon calculator, and see a classic aroid for semi-hydro on the Monstera deliciosa page.