You open a cupboard and something small and silver darts across the shelf and disappears into a crack before you can even register what it was.
Silverfish.
They’re one of the most common household pests in both the USA and Australia — yet most homeowners know almost nothing about them. They don’t bite. They don’t sting. They’re not dangerous to your health.
But leave them unchecked and they’ll quietly destroy your books, damage your wallpaper, eat holes in your clothing, and contaminate your stored food.
This guide covers everything you need to know to identify, eliminate, and prevent silverfish permanently.
What Exactly Are Silverfish?
Silverfish are small wingless insects named for their distinctive silver grey color and fish-like wriggling movement. They are:
- 12-25mm long as adults
- Silver to grey in color with a metallic sheen
- Fast moving with a distinctive wriggling motion
- Nocturnal — active at night and hiding during the day
- Extremely long lived for an insect — up to 8 years in ideal conditions
They have been around for over 400 million years making them one of the oldest insect species on earth. They survived whatever killed the dinosaurs. Which tells you something about how resilient they are.
Why Do Silverfish Come Into Your Home?
Silverfish are drawn to your home by three things:
Moisture
Silverfish need high humidity to survive. They are most commonly found in:
- Bathrooms
- Kitchens
- Laundry rooms
- Basements and subfloors
- Roof voids
Any area of your home with consistently high humidity is a potential silverfish habitat.
Food
Silverfish eat carbohydrates and proteins. In your home that means:
- Paper and cardboard
- Book bindings and wallpaper paste
- Stored flour, oats, and cereals
- Natural fabric fibres — cotton, linen, silk
- Dandruff and shed human skin flakes
- Glue and adhesives
Shelter
Silverfish prefer dark undisturbed spaces. They hide in:
- Behind walls and under flooring
- Inside wall voids and ceiling spaces
- In cardboard boxes and stacked paper
- Behind loose wallpaper
- Inside books that aren’t moved regularly
Signs You Have a Silverfish Problem
Because silverfish are nocturnal and fast moving many homeowners have a significant infestation before they realise it. Look for:
- Seeing silverfish at night when you turn on a light
- Small irregular holes in paper, books, or wallpaper
- Yellow staining on paper or fabric
- Small black pepper-like droppings near food sources
- Shed skin — silverfish moult throughout their lives leaving behind papery casings
How to Get Rid of Silverfish
Step 1 — Reduce Humidity
This is the most important step. Silverfish cannot thrive in low humidity environments. Target 50% relative humidity or below throughout your home.
Practical ways to reduce humidity:
- Run bathroom exhaust fans during and after every shower
- Fix any leaking pipes or taps immediately
- Ensure adequate subfloor ventilation — a common issue in Australian homes
- Use a dehumidifier in persistently damp rooms
- Open windows daily to allow air exchange
- Check roof gutters — blocked gutters cause moisture penetration into walls
A cheap digital hygrometer from any hardware store lets you monitor humidity in problem rooms. If it reads consistently above 60% you have a humidity problem that needs addressing.
Step 2 — Remove Food Sources
- Store all dried food — flour, cereals, pasta, rice — in airtight containers
- Don’t store cardboard boxes on the floor especially in damp areas
- Move books and papers off the floor and into sealed storage if not used regularly
- Vacuum regularly to remove skin flakes and food debris
Step 3 — Apply Diatomaceous Earth
Food grade diatomaceous earth is our top recommendation for silverfish elimination. It’s completely safe for humans and pets but deadly for silverfish. It works by damaging their exoskeleton causing them to dehydrate and die.
Apply a thin layer:
- Along baseboards in affected rooms
- Inside wardrobes and cupboards
- Under sinks and in bathroom cabinets
- In roof voids if accessible
- Along the edges of bookshelves
Replace after vacuuming or if it gets wet.
Step 4 — Use Silverfish Traps
Silverfish traps use a sticky surface combined with an attractant to catch silverfish. They are useful for:
- Confirming you have a silverfish problem
- Monitoring the success of your treatment
- Catching individual silverfish in low infestation situations
Place traps in corners, inside cupboards, and under sinks. Check weekly.
Step 5 — Apply Boric Acid
Boric acid is highly effective against silverfish. Apply a very thin layer — barely visible — along baseboards, inside wall voids if accessible, and in roof spaces.
Keep boric acid away from food preparation areas and out of reach of children and pets.
Step 6 — Use Essential Oil Repellents
Several essential oils repel silverfish effectively:
- Lavender oil — silverfish strongly dislike the scent
- Cedarwood oil — natural repellent and wood protector
- Clove oil — strong deterrent
- Peppermint oil — effective general insect repellent
Mix 10-15 drops with water in a spray bottle and apply to affected areas. Reapply weekly.
Cedar blocks and lavender sachets placed inside wardrobes and bookshelves provide ongoing passive repellent effect.
Step 7 — Seal Entry Points
Silverfish enter from outside and from wall voids. Reduce their access points:
- Seal gaps around pipes and cables
- Fix damaged weatherstripping around doors and windows
- Seal cracks in walls and baseboards with silicone caulk
- Check roof vents have intact fine mesh screens
Treating Specific Areas
Bathroom
The bathroom is the most common silverfish location. After reducing humidity with better ventilation:
- Apply diatomaceous earth along the back of under-sink cabinets
- Place lavender sachets inside bathroom storage
- Check and seal any gaps around pipes
Wardrobe and clothing storage
Silverfish damage natural fabric clothing — particularly items stored long term:
- Store seasonal clothing in sealed plastic bags or airtight boxes
- Place cedar blocks inside wardrobes
- Avoid cardboard storage boxes — use plastic sealed containers instead
- Wash stored clothing before returning to storage after the season
Bookshelves and paper storage
Silverfish love undisturbed books and paper:
- Move books regularly — silverfish avoid disturbed areas
- Store important documents in sealed plastic sleeves or folders
- Apply diatomaceous earth along the back edges of bookshelves
- Consider cedar shelf liners for valuable book collections
Roof voids and subfloors
If silverfish are present in roof voids or subfloors:
- Improve ventilation — install or upgrade vents
- Apply diatomaceous earth or boric acid if accessible
- Consider professional treatment for severe infestations in inaccessible areas
How Long Does Treatment Take?
With consistent treatment:
- Visible silverfish activity should reduce within 1-2 weeks
- Significant reduction in population within 3-4 weeks
- Complete elimination typically takes 6-8 weeks
The key is consistency. Treating once won’t solve the problem. Regular reapplication of diatomaceous earth combined with humidity reduction delivers lasting results.
Preventing Silverfish Coming Back
Once eliminated keep silverfish away permanently:
- Maintain indoor humidity below 50% year round
- Store all dried food in airtight containers permanently
- Keep cardboard storage off the floor
- Use cedar blocks in wardrobes and storage areas
- Apply diatomaceous earth along baseboards every 3 months as a preventative measure
- Fix any leaks or moisture issues promptly
When to Call a Professional
Call a professional pest controller if:
- Silverfish are present throughout multiple rooms despite treatment
- You suspect infestation inside walls or under flooring
- Treatment hasn’t reduced activity after 8 weeks
- You find significant damage to valuable items — books, documents, clothing
The Bottom Line
Silverfish are a moisture problem first and a pest problem second. Reduce the humidity in your home and you remove the conditions that allow them to thrive. Combine that with diatomaceous earth treatment and proper food storage and you have a highly effective silverfish elimination program that costs very little and uses no harsh chemicals.
Deal with the moisture. Apply the treatment. Be consistent.
You won’t see them again.
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