Chalk (Calcium Carbonate) Mushroom Supplement

Boost your mushroom yields with high-purity Calcium Carbonate, a vital supplement for balancing pH in mushroom substrates and casing layers. Commonly used in gourmet and medicinal mushroom cultivation, calcium carbonate helps maintain an ideal environment for healthy mycelial growth by buffering acidity and stabilising conditions.

✅ Essential for pasteurised substrates & casing mixes

✅ Supports optimal pH for species like oyster, lion’s mane & more

- pH Stabiliser – Helps maintain a stable, slightly alkaline pH, ideal for most mushroom species.
- Improved Mycelial Health – Creates a more hospitable growing environment, leading to faster colonisation.
- Contamination Control – Reduces the risk of mould and other unwanted organisms by managing acidity.
- Versatile Use – Suitable for use in a variety of growing mediums, including straw, coco coir, sawdust, and casing layers.

Add up to 3% Calcium Carbonate by dry weight of your substrate or casing layer. For example, add 30g of calcium carbonate per 1kg of dry substrate. Always mix thoroughly to ensure even distribution.


Note: Not a substitute for hydrated lime or gypsum. Use as part of a complete substrate preparation process.

250g – Great for hobbyists & small batches
500g – Ideal for regular growers
1KG – Cost-effective for ongoing projects
2KG – Best value for larger or frequent grows

• We ship from Tamborine Mountain, QLD using either AusPost or Aramex
• Fast dispatch within 1 business day (excluding Fridays) with express post options available