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Optional Extras in Vermicomposting

Section 8 of the Vermicomposting: Complete Guide
Picture of L.J.

L.J.

Environmental Advocate

Pumice
Thermometer
Lime
Moisture Meters
Horticultural Grit
Burlap
Egg Shells
pH litmus paper
Mineral Dust
Worm Treats
Lime
Crushed Eggshells
Crushed Oyster Shell
Natural Linen
Rock Dust
Additives
Rock Dust
Natural Linen
Mineral Dust
Moisture Mats
Pumice
Moisture Meter
Egg Shells
Mineral Dust
Oyster Shells
Basalt
Crushed Shells
Hessian
Back to Section 7: Harvesting Your Vermicast
Skip to Section 9: Vermicomposting Tips for Success

Contents

🧩 Optional Extras in Vermicomposting

While not essential, these extras can help fine-tune your worm bin, boost productivity, and make maintenance easier for beginners and pros alike.

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Lime Additives

In Vemicomposting, Lime typically refers to agricultural lime—a powdered form of calcium carbonate (CaCO₃).  

⚠️ Avoid Hydrated Lime

Never use hydrated lime (calcium hydroxide) in your worm bin.
It’s highly alkaline and can burn or kill worms, disrupt microbial balance, and damage castings.

Stick to agricultural lime (calcium carbonate) if you need to balance pH safely.

What Does Lime Do?

Lime can be used to balance pH levels and reduce acidity in the worm bin.

✅ Benefits of using Lime:

  • Neutralises acidity from food scraps like citrus, tomatoes, or fermented materials
  • Helps maintain a worm-friendly pH (around 6.5–7.5)
  • Can reduce odours and improve microbial activity
  • Supports healthy worm reproduction and casting production

 🧂 How Much Lime to Use?

  • Use sparingly-  a light sprinkle every few weeks is enough.
  • Monitor pH: use pH strips or a meter to avoid overcorrecting.
  • Watch your worms- if they’re trying to escape, it may signal pH imbalance

✅ You might need lime if:

  • Your bin smells sour or vinegary
  • Worms are sluggish or trying to escape
  • You’re adding acidic materials regularly
  • pH dips below 6.5 (if you test it)

❌ You don’t need lime if:

  • Your bin smells earthy and fresh
  • Worms are active and reproducing
  • You’re feeding a balanced mix of scraps
  • You’re using cardboard, paper, or crushed eggshells (which help buffer pH naturally)

🧂 Do You Need Lime in Vermicomposting?

No— lime is entirely optional. Use it only if your worm bin becomes too acidic and natural methods like adding crushed eggshells, cardboard, or balancing your scraps aren’t enough to manage the pH.

🧂 Lime Alternatives

While lime can help balance pH, there are gentler, worm-friendly options that often do the trick just as well—without risking overcorrection:

  • Crushed eggshells — provide a slow-release source of calcium to gently buffer acidity
  • Cardboard and paper bedding — naturally absorb excess acidity and maintain balance
  • Biochar (pre-charged) — helps stabilise pH and boosts beneficial microbial life
  • Balanced feeding — avoid overloading your bin with acidic scraps like citrus, tomatoes, or fermented foods

These natural methods support a thriving worm bin and keep your castings healthy. Use lime sparingly, only if signs of acidity persist.

corrugated cardboard
Egg Shells
Balanced feeding
corrugated cardboard
Ripped Up newspaper
Newspaper
corrugated cardboard
Shredded Paper

🛒 If You Want to Add Lime—Recommended UK Suppliers

If your bin needs a pH boost and natural methods aren’t enough, here are some trusted sources for agricultural lime (calcium carbonate):

Recommended Suppliers
⚠️ Always choose agricultural lime, not hydrated lime, and use sparingly. For smaller bins, crushed eggshells may be all you need.
🪱

🪵 Moisture Mats for Vermicomposting

A moisture mat, also known as a worm blanket, is a breathable cover placed directly over the bedding and scraps. It helps regulate humidity, reduce odours, and keep your worms comfortable and active.

This simple layer supports a healthy, balanced bin environment by retaining moisture evenly and preventing surface drying or crusting.

🛒 Purpose-Made or ♻️ Upcycled

You can use purpose-made moisture mats or get creative with upcycled materials. Good choices include:

  • Coconut coir mats — breathable and moisture-retentive
  • Jute fabric — natural and durable
  • Upcycled cotton cloths — soft and reusable

Just be sure to avoid synthetic or chemically treated materials, which could harm your worms or disrupt the composting process.

Burlap
Cotton Fabric Scraps
Coir Mat
Hessian
Coco Coir Block
Cotton
Natural Linen
Jute
Hemp

✅ Benefits:

  • Retains moisture evenly across the bin
  • Prevents dry patches and surface crusting
  • Blocks light and deters fruit flies
  • Encourages worms to feed near the surface

📏 How to Use:

  • Lay the mat flat over the bedding—no need to tuck or bury
  • Mist lightly if the bin feels dry
  • Replace or rinse as needed (every few weeks)

Recommended Suppliers:

Purpose-Made Moisture Mats

Material:

🛒  Supplier: Amazon UK- CRS Fur Fabrics Store

🛒  Supplier: Amazon UK- Discount Fabrics Ltd Store

🛒 Supplier: Wiggly Wigglers

If you’re using a common wormery brand, you may find a compatible moisture mat for your system here.

Can O Worms (Circular)
Tiger Wormeries (Square)
  •  

❓Are Moisture Mats a Requirement?

No-they’re optional, not essential. But, they’re a handy add-on for keeping your bin balanced—especially in dry rooms, heated homes, or during seasonal shifts.

Whether you use a purpose-made coir mat, upcycled cardboard, or a breathable fabric layer, they help retain humidity, reduce surface drying, and keep your worms comfortable. A simple tool for smoother composting, especially if you’re aiming for low-maintenance success.

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🍪 Worm Food or Treats

Some suppliers offer Worm Food or Treats as optional supplements designed to boost nutrition in your worm bin. These specially formulated blends provide balanced nutrients that help maintain worm health and support steady growth—especially useful when natural scraps are limited or during slower seasons.

Typical Ingredients

Typical Ingredients:

  • Grains like maize, wheat, and soya
  • Nutrient-rich additives to support worm development
  • Sometimes natural binders or slow-release nutrients

When to Use:

  • To maintain worm populations when food waste is limited
  • During colder months when decomposition slows
  • For commercial or large-scale wormeries needing consistent feeding

How to Use:

  • Sprinkle a handful evenly over the top layer of moist bedding
  • Moisten if the surface feels dry
  • Reapply when fully consumed, avoiding overfeeding to prevent mould

❓Is it a Necessity?

No-Worm Food/Treats aren’t essential, but it’s a useful supplement—especially for beginners, resets, or bins with limited food variety. If you’re curious, try it in small amounts and observe how your worms respond.

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🪨🧂🌱 Optional Extras:
Rock Dust, Mineral Dust, Horticultural Grit, & Crushed Oyster Shells

These materials can be added to your worm bin to support digestion, balance pH, and enrich castings. They’re not essential- but they offer useful benefits when used correctly. 

What do we mean by 'Grit'?

Grit consists of tiny, hard particles that worms store in their gizzard to help grind and break down food efficiently inside their digestive system.

🪨 Rock Dust: Nature’s Mineral Booster for Your Worm Bin

Rock dust is finely ground volcanic or igneous rock, packed with essential trace minerals like calcium, magnesium, and iron.

✅ Benefits of Rock Dust in Worm Bins

  • 🥚 Acts as Grit to Aid Worm Digestion
  • 🧃 Buffers Acidity
  • 🌱 Improves Castings Quality
  • 🪱 Supports Microbial Activity
  • 🧺 Enhances Bin Resilience
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Rock Dust
Granite
Pumice
Basalt
When to Use

⌚When to Use Rock Dust

  • Add it if your bin needs extra mineral support, especially during resets, periods of low activity, or when feeding acidic scraps.
  • It’s best used sparingly and strategically—not as a routine additive.
  • It pairs well with eggshells or mineral dust for a balanced grit and buffering mix.

How to Use Rock Dust

  • Occasionally, sprinkle 1–2 tbsp per feeding layer or 10L bedding.
  • Best only to used during resets or acidic feeds.
  • Use sparingly and only when needed- too much can dry out your bin or overwhelm your worms.

🛒 Supplier: Elixir

🛒 Supplier: Wiggly Wigglers

🛒 Supplier: Gardening Naturally

🧂 Mineral Dust

Mineral dust refers to finely ground powders made from natural or refined minerals—such as lime, gypsum, or volcanic blends. 

✅ Benefits in Worm Bins

  • 🧃 Buffers Acidity
  • 🌱 Adds Trace Minerals
  • 🪱 Supports Microbial Life
  • 🧺 Improves Bin Resilience
  • 🧴 Prepares Castings for Soil Use

Mineral Dust
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When to Use

🧂 Mineral Dust: When to Use

  • Use occasionally to buffer acidity and enrich castings
  • Ideal during feeding of acidic scraps or bedding refreshes
  • Add when worm activity slows or bin smells sour
  • Pair with rock dust or eggshells for balanced mineral mix

How to Use Mineral Dust

  • Sprinkle 1–2 teaspoons per feeding layer or bedding refresh
  • Use sparingly, not with every feed
  • Ensure bedding is moist before application
  • Combine with eggshells or rock dust for best effect

🛒 Supplier: Original Organics

🛒 Supplier: Elixir Gardens

🌱 Horticultural Grit

Horticultural grit is a coarse, inert material made from crushed stone—typically silica or flint. 

✅ Benefits in Worm Bins

  • 🥚 Acts as Grit to Aid Worm Digestion
  • 💨 Improves Bedding Texture
  • 🚿 Enhances Drainage
  • 🧺 Boosts Bin Resilience
  • 🧱 Inert & Long-Lasting

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Horticultural Grit (2)
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When to Use

⌚ Horticultural Grit: When to Use

  • Use to improve bedding texture and airflow
  • Ideal during resets or when bedding feels soggy or compacted
  • Add when worm digestion needs extra grit support
  • Pair with eggshells or moist bedding for balance

How to Use Horticultural Grit

• Mix a small handful into bedding or sprinkle with food layers
• Use as needed—not every feed
• Choose fine-grade (1–4 mm), washed, lime-free grit
• Avoid sharp or dusty types that may irritate worms

🛒 Supplier: Melcourt

🛒 Supplier: Vitax

🛒 Supplier: Muddy Hands Store

🐚 Crushed Oyster Shells 

Crushed oyster shells are a slow-release source of calcium carbonate, offering both digestive grit and gentle pH buffering in worm bins. 

✅ Benefits in Worm Bins

  • 🥚 Acts as Grit to Aid Worm Digestion
  • 🧃 Buffers Acidity
  • 🌱 Mineral Enrichment 
  • 🧺 Long-Lasting 

When to Use

⌚Crushed Oyster Shells: When to Use

  • Use to buffer acidity and support worm digestion
  • Ideal during resets or when feeding fermented or citrus scraps
  • Add when castings need calcium enrichment or bin resilience
  • Pair with eggshells or mineral dust for balanced mineral support

How to Use Crushed Oyster Shells

  • Crush finely or use poultry-grade oyster shell grit
  • Sprinkle 1–2 tablespoons per feeding layer or bedding refresh
  • Use occasionally—not with every feed
  • Combine with eggshells or rock dust for long-term bufferin

🛒 Supplier: Maltby’s Store

🛒 Supplier: AB Tools

🛒 Supplier: Henry Bell

🥚Crushed Eggshells

Eggshells are a free, natural source of calcium carbonate that support worm digestion and help buffer acidity in your bin. When dried and crushed, they act as gentle grit and slow-release mineral enrichment—ideal for balancing soft, acidic food scraps.

✅ Benefits in Worm Bins

  • 🥚 Acts as Grit to Aid Worm Digestion
  • 🧃 Buffers Acidity
  • 🌱 Adds Calcium to Castings
  • 🧺 Improves Bin Resilience
  • 🆓 Free & Upcycled

When to Use

⌚Crushed Eggshells: When to Use

  • Use regularly to support digestion and buffer acidity
  • Ideal when feeding soft, wet, or acidic scraps
  • Add during resets or when castings need calcium enrichment
  • Pair with oyster shells or rock dust for balanced mineral support

🥚 How to Use Crushed Eggshells

  • Rinse, dry, and crush finely before use
  • Sprinkle with food scraps or mix into bedding
  • Use 1–2 tablespoons per feeding layer
  • Combine with other grit sources for best effect- great with oyster shell or rock dust for balance.

❓ Are Rock Dust, Mineral Dust, Shells & Grit Needed in Your Worm Bin?

These extras are not essential for worm survival but can significantly boost your bin’s health and output when used thoughtfully.

Adding crushed eggshells is a simple, free, and sustainable way to provide gentle grit and calcium carbonate to your worm bin. They help with digestion, buffer acidity, and enrich your castings naturally.

However, if you don’t have access to eggshells or prefer to keep things vegan, you can substitute with alternative grit sources such as horticultural grit, crushed granite, or other plant-based mineral options to support your worms’ grinding process without animal products.

🔍 Click to Enlarge Image
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🧰 Optional Extra Equipment for Worm Bin Monitoring

While you don’t need fancy tools to run a healthy worm bin, a few optional extras can make monitoring easier and more precise. If you’re curious about moisture levels, pH balance, or seasonal temperature shifts, these tools can help you spot issues early and fine-tune your setup with confidence. Ideal for troubleshooting, teaching, or simply levelling up your vermicomposting game.

 💧 Using a Moisture Meter in Vermicomposting

A moisture meter helps you check if your worm bin is too wet, too dry, or just right—without guesswork or messy hands.

Why Monitor Using a Moisture Meter

✅ Why Use a Moisture Meter:

  • Ensures optimal moisture (like a wrung-out sponge)
  • Prevents anaerobic conditions and bad smells
  • Helps avoid dry zones that slow decomposition
  • Useful for beginners and classroom setups

💧 Ideal Moisture Range

Look for readings in the 40–60% range 

📏 How to Use:

  • Insert the probe into different areas of the bin
  • Adjust by adding water (if dry) or bedding (if wet)
  • Clean the probe after use to prevent corrosion

🛒 Supplier: Antonki

🛒 Supplier: Yizerel

🌡️ Temperature Monitoring in Vermicomposting

Worms thrive in moderate temperatures—too hot or too cold can slow decomposition or harm your colony.

Why Monitor Temperature

✅ Why Monitor Temperature:

  • Ensures worms stay active and healthy
  • Helps prevent overheating in summer or freezing in winter
  • Useful for outdoor bins, Bokashi integrations, or school setups
  • Supports seasonal adjustments to feeding and bedding

📏 Ideal Temperature Range:

  • 10–25°C (50–77°F) is the sweet spot
  • Below 10°C: worms slow down
  • Above 30°C: risk of stress or die-of

🧪 How to Monitor:

  • Use a soil thermometer or a multi-function meter with a temperature probe
  • Check different zones—especially near fresh scraps or bedding
  • Adjust by insulating, relocating, or tweaking airflo

🛒 Supplier: Stronrive

🛒 Supplier: Woodside

🟢 pH Monitoring in Vermicomposting

Worms and microbes thrive in a slightly acidic to neutral environment.

If pH drifts too far, it can cause:

  • Worm stress or die-off
  • Slower decomposition
  • Smelly, sour bins
  • Poor-quality castings

Why Monitor pH

✅ Why Monitor pH

  • Monitoring pH helps you catch issues early and adjust with safe, worm-friendly methods.

📏 Ideal pH Range

  • 6.5 to 7.5 is the sweet spot
  • Below 6.0: too acidic—risk of worm escape or inactivity
  • Above 8.0: too alkaline—can harm microbes and castings

🧪 How to Monitor pH

  • Use a soil pH meter (standalone or part of a 4-in-1 tool)
  • Insert the probe into moist bedding or near fresh scraps
  • Take readings from multiple zones for accuracy
  • Clean the probe after use to prevent corrosion

For occasional checks, pH test strips or liquid soil kits also work well.

🛒 Supplier: Lansonee

🛒 Supplier: Boltsafe

🛒 Supplier: Original Organics

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Beginner-Friendly Monitoring Tools for Wormeries

If you want a single, easy-to-use device to measure pH, moisture, and temperature, soil meters are a great choice. Below, we’ve included two practical options: one battery-operated and one rechargeable, both ideal for beginners and small worm bins.

Recommened Item

🛒 Supplier: Yamron (battery operated) 🔋

  • 4-in-1 Soil Moisture Meter 
    Measures: Temperature / Soil Moisture / pH / Sunlight Intensity
    💷 Price Range: ~£20
    🔧 Simple interface, ideal for beginners and small wormeries

🛒 Supplier: Loxiia (rechargable)🔌

  • 4-in-1 Moisture Meter for Plants
    Measures: pH / Moisture / Light / Temperature
    🌀 Features: 180° Flex Neck for easy reading
    💷 Price Range: ~£20
    🔋 Rechargeable and portable

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🔗 Handy Bundles Featuring Multiple Optional Extras

To make it easier and more cost-effective, we’ve gathered some bundles that combine two or more of the helpful accessories and tools mentioned throughout this guide.

Recommended Suppliers

🛒 Supplier: Wiggly Wigglers

🛒 Supplier: Original Organics

🛒 Supplier: Wormcity

🛒 Supplier: Yorkshire Worms

🌟 Ready to Boost Your Worm Bin?

If you’re looking to get the best results with your worm composting, these top tips will guide you toward a thriving, balanced system. For detailed advice on keeping your wormery happy and productive, see Section 9: Top Tips for Success.

Section 9: Top Tips for Success
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