• 250g Bag of Calcium Carbonate (Chalk) For pH Balancing Mushroom Substrate
  • Dish of Calcium Carbonate For Maintaining Healthy pH In Mushroom Substrate
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Calcium Carbonate (Chalk) Mushroom Supplement

Calcium Carbonate (Chalk) Mushroom Supplement

$7.00
$7.00
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Benefits

- 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.

How do I use it?

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.

Delivery Information

  • We ship from Tamborine Mountain, QLD using either AusPost or Aramex
  • Fast dispatch within 1-2 business day (excluding Fridays) with express post options available
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Calcium Carbonate — commonly known as chalk — is one of the most reliable and widely used supplements in mushroom cultivation. Its primary role is as a pH buffer: as mycelium colonises a substrate, it produces acids that can gradually push the pH into a range that inhibits growth or invites contamination. A small addition of calcium carbonate keeps the environment stable, giving your mycelium the consistent conditions it needs to colonise fully and fruit well.

What it does in your substrate

Buffers pH: counteracts the natural acidification that occurs during colonisation, maintaining a more stable and mycelium-friendly environment throughout the grow.

Adds calcium: calcium is an essential mineral for fungal cell wall development and helps mycelium grow stronger, denser, and more resilient.

Reduces contamination risk: a stable, slightly alkaline substrate is a less welcoming environment for many competing moulds and bacteria, helping your mycelium get established before contaminants can take hold.

Where to use it

Calcium carbonate is suitable for sterilised and pasteurised bulk substrates, casing mixes, and grain spawn. It's particularly useful in supplemented hardwood substrates (Masters Mix and similar) where higher nitrogen content can accelerate acidification. Recommended at 0.5–1% by dry weight of your substrate mix.

It's also excellent in garden applications — a gentle, slow-release source of calcium for vegetable beds, raised planters, and pots where pH drift is a concern.

Available sizes

Available in 100g, 250g, 500g, and 1KG bags — scaled for hobbyist to small commercial grows. Sourced and packed in Australia.

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