How to Get Rid of Fish Moths: Protect Your Home from Silent Damage

They move at night. They avoid light. They’re rarely seen, even when present in significant numbers. And by the time most Australian homeowners notice the damage they cause, they’ve been active in the home for months – quietly feeding on books, clothing, wallpaper, and stored items in the dark corners of wardrobes, bookshelves, and cupboards.

Fish moths – known scientifically as silverfish (Lepisma saccharinum) and sometimes called bristletails or paper fish – are one of Australia’s most widespread household pests. There is no real pest season for silverfish in Australia as they live indoors. Certainly warmer weather allows them to breed more quickly, but it is humidity that is critical for their survival. They need a relative humidity of between 75% and 95%.

They cause no harm to humans. But the damage they cause to property is real, progressive, and largely irreversible once it has occurred.

What Exactly Are Fish Moths?

Fish moths are primitive, wingless insects – one of the oldest insect lineages on Earth, largely unchanged for over 400 million years. Their common name comes from their appearance and movement: a tapered, silvery body that tapers from a broad head to a narrow posterior, covered in tiny scales, and a rapid wriggling motion when disturbed that resembles a swimming fish.

They have a distinctive tapered shape with three tail-like appendages, giving them a unique appearance. Their size can range from 12 to 30mm and their body is shaped like a teardrop.

Key identifying features:

• Colour: Silver to grey, sometimes with a slight brownish wash
• Size: 12-20mm body length when fully grown
• Movement: Very fast, erratic scurrying when exposed to light
• Distinctive features: Three long bristles at the rear and two long antennae at the front

Silverfish can survive in all climates but prefer dark or damp areas. In Australian homes, they’re most commonly found in bathrooms, kitchens, wardrobes, roof voids, subfloors, and anywhere that books, paper, or fabric is stored.

What Fish Moths Eat – and What They Damage

Understanding what fish moths eat is essential to understanding where to look for them and what they’re damaging in your home.

Their diet consists of materials rich in sugars or starch – so if you’re wondering what silverfish eat, the answer includes glue in books, linen, paper, and silk clothes.

More specifically, fish moths feed on:

Books and paper. Silverfish cause damage to books and paper by feeding on the surface and whilst they don’t have strong mouthparts they tend to abrade a surface until they break through, as can be evidenced by an almost lace-like appearance on a book cover for example. Older books with natural-paste binding glue are particularly vulnerable.

Clothing and fabrics. Fish moths are especially attracted to items that contain starches – your cottons, linens, and silks are what they would typically go for. They wreak havoc by chewing their way through materials, creating small, irregular holes as they go.

Wallpaper. The starch in wallpaper paste is a direct food source. Fish moths feeding on wallpaper from behind cause bubbling, lifting, and eventual damage to the surface.

Stored foods. Dry goods including flour, rolled oats, dried pasta, and cereals stored in original packaging are vulnerable – fish moths can chew through cardboard and thin plastic packaging.

Photographs and documents. The gelatin and paper combination in photographs is a target. Important documents in paper files are similarly vulnerable to long-term feeding damage.

Signs You Have Fish Moths in Your Home

Silverfish are nocturnal, meaning they’re most active at night. You may see them scurrying in bathrooms or pantries when the lights are turned on suddenly in the dark.

However, seeing a live fish moth is not the most common way Australians discover an infestation. Look for:

Yellow staining. Even if you don’t notice actual skin molts, you may see the yellow dust left behind on surfaces as silverfish molt. These yellow stains often show up in books, papers, cardboard boxes, or on clothing.

Irregular holes or surface abrasion. Holes in stored clothing, particularly cotton, linen, or silk items, with slightly unravelling edges. Surface feeding on book covers or paper that appears scratched or abraded.

Small dark pellets (frass). Silverfish will leave behind a small pelletised frass which resembles small mouse droppings and this may be scattered randomly under items or on surfaces.

Shed skins. Fish moths moult repeatedly throughout their lives. Pale, translucent shed skins found in wardrobes, bookshelves, or behind furniture are a direct indicator of ongoing activity.

What Attracts Fish Moths to Your Home

Silverfish are attracted to dark, humid environments and food sources like paper, glue, and fabrics. Leaky pipes, poor ventilation, and cluttered spaces provide ideal conditions for them to thrive.

The specific conditions that most commonly support fish moth infestations in Australian homes include:

Humidity. Bathrooms with inadequate ventilation, laundries, kitchens, and subfloor areas with damp soil or poor airflow are the primary habitat drivers. As silverfish like moist/high humidity environments, reducing humidity in susceptible areas is the key to prevent a silverfish problem; use de-humidifiers, air-conditioning and fans in bathrooms, kitchens, laundries, roof voids, sub-floors and any other damp areas.

Clutter and undisturbed areas. Wardrobes full of rarely-worn clothing, bookshelves that aren’t regularly moved, and storage boxes in dark corners all provide the undisturbed, dark harbourage that fish moths prefer.

Cardboard boxes. Cardboard is both a food source and a harbourage material. The ingress of silverfish into Western Australian homes is quite often done by bringing in cardboard cartons, books and papers from infected sites.

Old books and paper. Accumulated books – particularly older volumes with natural-paste binding – are a reliable, long-term food source that sustains fish moth populations.

DIY Control Measures

The following measures reduce fish moth populations and deter new activity, though they rarely fully eliminate an established infestation:

Reduce humidity. Fix any leaking pipes under sinks, ensure bathroom and laundry exhaust fans work effectively, and consider a dehumidifier in storage areas during humid periods. This addresses the primary environmental driver.

Diatomaceous earth. Sprinkle food-grade diatomaceous earth along your bookshelf. You can also do so along baseboards and other areas where fish moths are active. The substance dehydrates and kills them. You can also place silica gel packs between books on your shelf to absorb moisture and keep them dry.

Cedar products. Cedar oil and cedar products act as natural repellents. Cedar oil is one of the many essential oils used to get rid of silverfish, and is an especially effective pest killer for silverfish, clothes moths, and carpet beetles.

Seal entry points. Fish moths can enter homes through cracks, gaps around windows and doors, and other small openings. Sealing these reduces introduction from outside.

Store vulnerable items correctly. For clothing items that you don’t wear frequently, store them in airtight plastic containers or vacuum-sealed bags to avoid landing up with damage. Move books and documents from cardboard boxes into sealed plastic storage.

Heat treatment for small items. If the clothes and belongings are not susceptible to heat, place in a black plastic bag, seal and leave in the sun for 1-2 hours. The heat will kill any silverfish and eggs on the clothes.

When Professional Treatment Is Needed

DIY measures work well as prevention and can suppress light activity. For established infestations – particularly those that have been active long enough to cause visible damage – professional treatment reaches the areas DIY products don’t.

Professional silverfish treatment usually involves applying a fine film of dust that contains a small amount of pesticide. This is lightly misted throughout roof voids, under and behind benches and cupboards.

Mr Pest Controller’s licensed technicians treat silverfish (fish moths) as part of the standard general pest treatment, covering cockroaches, ants, spiders, and silverfish in a single professional visit. The treatment reaches roof voids, subfloor areas, internal wall cavities, and all harbourage areas that surface sprays never access.

Starting from $220 for a standard Australian residential property.

Book a professional fish moth treatment with Mr Pest Controller