Choosing the correct type of diatomaceous earth is important because products intended for garden and property applications differ significantly from materials manufactured for swimming-pool filtration. Soil Solutions supplies Food-Grade Diatomaceous Earth – Perma-Guard Fossil Shell Flour in several sizes for appropriate garden, property and animal-environment applications.
Food-grade and pool-grade diatomaceous earth may originate from the same type of naturally occurring mineral deposit, but differences in processing can substantially change their composition and intended use.
This guide explains the difference between food grade and pool grade and how the two grades differ, what amorphous and crystalline silica mean, and what to check before buying diatomaceous earth in Australia.
What Is Diatomaceous Earth?
Diatomaceous earth, commonly shortened to DE, is a naturally occurring material formed from the fossilised remains of microscopic aquatic organisms called diatoms.
Diatoms develop silica-rich shells. When they die, their remains can accumulate on the beds of ancient lakes and waterways. Over a very long period, these deposits form a lightweight, porous mineral material that can be mined, dried and milled into a fine powder.
Diatomaceous earth may also be called:
- DE
- Diatomite
- Fossil shell flour
- Diatom powder
- Amorphous silica powder
However, these descriptions do not automatically mean that every product has the same composition or is suitable for the same purpose.
Why Are There Different Grades of Diatomaceous Earth?
Diatomaceous earth can be processed in different ways depending on its intended application.
Some products are minimally processed and retain a high proportion of amorphous silica. Other forms are subjected to high temperatures to alter their physical and filtration properties.
These processing differences produce two broad categories commonly encountered by consumers:
- Food-grade diatomaceous earth
- Pool-grade or filter-grade diatomaceous earth
Despite their similar appearance, these grades are not interchangeable.
What are Food-Grade Diatomaceous Earth Products?
Food-grade diatomaceous earth is generally uncalcined and consists predominantly of amorphous silica. It is milled into a fine powder and must meet the specifications relevant to its stated grade and intended application.
The term diatomaceous earth food grade describes the product’s composition, purity and suitability for particular regulated applications. It does not mean that all products carrying this description are approved for every possible food, animal, household or pest control use.
Depending on the product and its label, food grade powder diatomaceous earth may be used in areas such as:
- Gardens and horticultural environments
- Soil-management routines
- Dry storage and property-maintenance areas
- Animal housing and bedding environments
- Moisture and odour-management applications
- Certain agricultural processes
Always check the product label before use. The directions supplied with the specific product take priority over general advice found online.
What is Pool-Grade Diatomaceous Earth?
Pool-grade diatomaceous earth is manufactured specifically for filtration.
During production, the raw diatomaceous material is typically calcined, meaning it is heated to a high temperature. This alters the structure of the silica and creates characteristics that make the material useful for filtering very fine particles from swimming-pool water.
The heating process also increases the proportion of crystalline silica within the material. Crystalline silica presents a more serious inhalation hazard than amorphous silica, particularly when fine particles become airborne. Crystalline silica should not be taken internally.
Pool-grade DE is intended for use inside compatible pool-filtration systems. It should not be substituted for food-grade diatomaceous earth in gardens, around animals, inside the home or in other general-purpose applications.
Food-Grade vs Pool-Grade Diatomaceous Earth
|
Feature |
Food-grade diatomaceous earth |
Pool-grade diatomaceous earth |
|
Typical processing |
Generally dried, milled and uncalcined |
Heat-treated or calcined |
|
Predominant silica form |
Amorphous silica |
May contain a substantially higher proportion of crystalline silica |
|
Primary purpose |
APVMA-approved insecticide and food additive anti-caking agent. |
Swimming pool and industrial filtration |
|
Appearance |
Fine, light-coloured powder |
Fine, light-coloured filtration powder |
|
Suitable for garden use |
Only when permitted by the product label |
No |
|
Suitable for pool filtration |
No, unless specifically manufactured and labelled for it |
Yes, in compatible filtration systems |
|
Dust precautions required |
Yes |
Yes, with greater concern around respirable crystalline silica |
|
Can one replace the other? |
No |
No |
The products can look very similar, so appearance alone is not a reliable way to identify the correct grade.
What is Amorphous Silica?
Perma guard is 89-95% Silicon Dioxide. Crystaline Silica in Perma guard is less than 0.5%. This is what makes it unique in regard DE with the absence of negative contaminants.
Silica is a compound made from silicon and oxygen. It occurs naturally in several different structural forms.
Amorphous silica has a less ordered molecular structure than crystalline silica. Most natural, uncalcined diatomaceous earth consists predominantly of this amorphous form.
This distinction matters because amorphous silica is generally considered less hazardous than respirable crystalline silica. Nevertheless, amorphous diatomaceous earth is still a very fine and potentially irritating dust.
Safe Work Australia notes that crystalline silica is generally more hazardous than non-crystalline or amorphous silica. Regardless of grade, users should avoid generating or breathing airborne dust.
What is Crystalline Silica?
Crystalline silica has an organised crystal structure and includes forms such as quartz and cristobalite.
Heating amorphous silica to sufficiently high temperatures can convert some of it into crystalline forms. This is one reason the silica composition of calcined pool-grade DE can differ considerably from that of uncalcined food-grade material.
Long-term or repeated exposure to respirable crystalline silica can cause serious lung disease. Pool-grade diatomaceous earth should therefore only be handled and used according to its filtration instructions and safety data sheet.
Food-grade DE may still contain a small naturally occurring amount of crystalline silica. “Food grade” should never be interpreted as meaning that the dust is safe to inhale.
What is Fossil Shell Flour?
Fossil shell flour is another name commonly used for finely milled, food-grade diatomaceous earth.
Fossil shell flour is sourced from extremely pure, fresh water deposit of the diatom Melosira praeislandica whose shell is made of amorphous silica. It’s shape and hardness are important to how it works on exo skeleton insects.
The name refers to the microscopic fossilised shells from which the material is formed. These shells are not the remains of shellfish such as prawns, crabs or oysters. They come from diatoms—microscopic aquatic organisms with silica-based structures.
Perma-Guard Fossil Shell Flour is derived from a freshwater diatomaceous earth deposit. According to its product specifications, it consists predominantly of amorphous silica and contains naturally occurring trace minerals.
The term “fossil shell flour” does not replace the need to read the label. Buyers should still confirm the grade, composition and intended applications of the specific product.
How to Identify the Right Diatomaceous Earth
Before purchasing diatomaceous earth, inspect the product description and packaging carefully.
Look for information confirming:
- Whether the product is food-grade or filter-grade
- Whether it is calcined or uncalcined
- Its amorphous and crystalline silica content
- The applications for which it is intended
- Clear directions and safety precautions
- The manufacturer or supplier
- Appropriate storage instructions
Avoid products sold in unmarked containers or bags with incomplete descriptions. A vague online listing may not provide enough information to determine the product’s grade or composition.
If the packaging refers to pool filtration, filter media, calcined DE or industrial filtration, it should not be used as a substitute for food-grade diatomaceous earth.
Can Pool-Grade DE Be Used in the Garden?
No. Pool-grade diatomaceous earth should not be used on plants, in garden beds, in compost or around animal environments.
It is engineered for filtration and can contain substantially more crystalline silica than food-grade DE. Its composition and processing make it unsuitable for general garden applications.
Having some pool-grade DE left over after changing a filter does not make it appropriate for another purpose. Follow the manufacturer’s instructions for handling and disposal.
Can Food-Grade DE Be Used in a Pool Filter?
Food-grade DE should not be placed in a pool filter unless the manufacturer of both the product and filtration system specifically approves it.
Pool filtration depends on materials with particular particle sizes and filtration characteristics. A general-purpose food-grade fossil shell flour may not operate correctly in the system and could reduce filtration performance or damage equipment.
Use only the filtration medium specified by the pool-filter manufacturer.
Does “Food Grade” Mean It Is Safe to Eat?
The expression “food grade” can be misleading when it is taken out of context.
It does not mean every food-grade DE product should be consumed. Regulations and approved uses vary between countries, products and applications. A product sold for garden, property or animal-environment use should not automatically be treated as a human dietary supplement.
Many American veterinary Universities have performed autopsies on animals fed with DE in their rations. All organs were in perfect health everywhere.
Use the product only for purposes stated on its packaging. Seek advice from a qualified health professional before consuming any supplement or substance promoted for health purposes.
Handling Food-Grade Diatomaceous Earth Safely
Food-grade DE is predominantly amorphous silica, but it remains a very fine mineral powder. Sensible dust precautions should always be followed.
When handling it:
- Read and follow the product directions
- Avoid breathing airborne powder
- Apply it in calm conditions
- Consider suitable respiratory protection when dust could become airborne
- Wear eye protection where necessary
- Avoid direct contact with the eyes
- Keep children and animals away during application
- Wash your hands after handling it
- Keep the container sealed when not in use
- Store it somewhere cool and dry
Avoid throwing, sweeping or pouring the product in a way that creates a visible dust cloud. A light, controlled application is easier to manage than large piles of powder.
How Diatomaceous Earth Works on Insects
Diatomaceous earth is commonly associated with the management of crawling insects, including fleas and bedbugs. When susceptible insects come into direct contact with dry diatomaceous earth, the fine mineral particles can absorb oils and damage the protective waxy layer of their exoskeleton. This causes moisture loss and gradual dehydration rather than poisoning the insect through a conventional insect control using chemical action.
Its effectiveness depends on direct contact and dry conditions. Diatomaceous earth should not be considered a complete or immediate solution for serious flea or bedbug infestations. Bedbugs can hide deep inside furniture, wall gaps and mattresses, while fleas may continue developing in carpets, bedding, and animal environments. Professional pest-control assistance may be necessary for established infestations. So long as the DE is present it will continue to kill new hatchlings.
Only use a product specifically labelled and approved for the intended pest-control application. Follow its directions carefully, avoid creating airborne dust and never substitute pool-grade diatomaceous earth for an appropriate food-grade or pest-control product.
Frequently Asked Questions
Are food-grade and pool-grade diatomaceous earth the same?
No. Food-grade DE is generally uncalcined and predominantly composed of amorphous silica. Pool-grade DE is heat-treated for filtration and may contain a much higher proportion of crystalline silica.
Can I tell the grades apart by looking at them?
Not reliably. Both can appear as fine, pale powders. Check the packaging, product specifications and safety information instead of relying on appearance.
Is amorphous silica completely harmless?
No fine dust should be treated as completely harmless. Amorphous silica is generally considered less hazardous than crystalline silica, but airborne food-grade DE can still irritate the nose, throat, lungs, skin and eyes.
Is all fossil shell flour food-grade?
The term is commonly associated with food-grade diatomaceous earth, but you should still confirm the product’s grade and intended uses from its packaging.
Can I replace pool-grade DE with food-grade DE in my filter?
Not unless the filter manufacturer specifically permits it. Food-grade fossil shell flour may have different particle and filtration characteristics.
Can pool-grade DE be used around plants?
No. Pool-grade DE is manufactured for filtration and should not be applied to plants, soil, compost or animal environments.
Should I wear a mask when handling food-grade DE?
Appropriate respiratory protection should be considered whenever the fine powder could become airborne. Always follow the safety instructions supplied with the product.
Where can I buy food-grade diatomaceous earth in Australia?
Soil Solutions supplies Perma-Guard Food-Grade Diatomaceous Earth online in a selection of sizes. Check the product information and choose a quantity appropriate for your intended application.
Choose the Grade That Matches the Application
Food-grade and pool-grade diatomaceous earth may share a natural origin, but processing gives them very different compositions and purposes.
Food-grade fossil shell flour is generally uncalcined and predominantly composed of amorphous silica. Pool-grade material is heat-treated to create an effective filtration medium and can contain higher concentrations of crystalline silica.
Neither product should be substituted for the other.
Before buying or using DE, read the complete label, confirm its grade and ensure that your intended application is covered by the manufacturer’s directions.
Explore the available sizes of Perma-Guard Food-Grade Diatomaceous Earth from Soil Solutions.