# Diatomaceous Earth in Substrate?



## Peterstunt (Jan 10, 2014)

You could just sell me the scuds


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## lochaber (Jan 23, 2012)

I think the DE is so fine it would get stirred up into the water column and make a mess out of the tank.

I'm not certain, but I've heard one of the explanations for DE working is that it scrapes up the insect's cuticle, and then it dehydrates. I don't think this would work in an aquatic environment, but there might be other osmotic type problems.

I don't think the water would affect the DE, diatom skeletons are silica, which is effectively insoluble in water. They are just like little microscopic pieces of broken glass.


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## mistergreen (Dec 9, 2006)

De doesn't work wet. It turns to clay.


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## GraphicGr8s (Apr 4, 2011)

xenxes said:


> Had a random thought for possible scud control.
> 
> Would diatamaceous earth mixed into the substrate in an aquarium function the same way in terrestrial soil? i.e. would it cut into the scud's exoskeleton and thereby expose it to microorganisms in the substrate which kill it?
> 
> Or would being in water render diatamaceous earth soft and soggy, i.e. no longer sharp enough to cut into a paper bag? *How do moisture affect diatoms on the microscopic level?*


DE is not a living organism. 

Left in the water I've found everything stirs it up and makes a mess. Not good as any part of a substrate. It makes a great filter though. Just don't let it get into a normal filter.


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## xenxes (Dec 22, 2011)

@lochaber thanks for reminding me that they're silicate which is water insoluble. I would think that means, on the microscopic level, they would still retain their sharpness and jaggedness even though to us they feel like clay when wet.

Thus I would presume when mixed into the substrate, these tiny sharp particles would cut into whatever crawled through it, i.e. it might harm scuds, but also beneficial nematodes too. I don't know if the pros outweigh the cons... I think I'll just have to test it out.

The buffering capacity is nice too, kind of like charcoal or activated carbon, i.e. after saturating it with enough nutrients plant roots may be able to leech it back at a slow rate for years to come.


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## scx (Sep 8, 2013)

DE used to be microorganisms, they are usually the shells of diatoms, which are from the ocean. It kills insects by cutting them and dehydrating them. It would not work the same in an aquarium.


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## xenxes (Dec 22, 2011)

Well I did some further reading, since various web sources suggest different modes of action. Most are just hearsay and nutraceutical BS saying the same thing about the sharpness cutting bugs up, and cutting parasites up in your intestines if you eat them.

Basically, the most widely accepted mode of action is that the DE absorbs the waxy layer and moisture from an insect's body and they die from desiccation (the cutting them apart with with tiny glass shards was not mentioned in the below authoritative articles). If this is the case then DE would not work in water.



> Proposed modes of action
> Several proposed modes of action for inert dusts have been extended by various
> researchers. They are: 1) inert dusts block spiracles and insects die from
> asphyxiation, 2) dusts lodging between cuticular segments increase water loss
> ...


http://www.ksre.ksu.edu/grsc_subi/T...ure_slides/GRSC651_lect_20(1)_Inert_Dusts.pdf

Here's another about ingesting food grade DE:



> The action of diatomaceous earth on parasites is unclear but it has been suggested
> that the abrasive action of the powder pierces or scratches the outer protective layer of invertebrates
> including internal parasites, resulting in death by dehydration. However, diatomaceous earth is also
> rich in trace elements and it may be the enhanced nutritional status of the animals that has allowed
> ...


http://www.mtsylviadiatomite.com.au/mod/files/research/DE_Natural_Dewormer_Study.pdf

That said it probably isn't good for scud control. However, the buffering capacity makes it seem desirable for retaining nutrients in the substrate, and silicon is an important micronutrient. So I'm still putting it in!


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## lochaber (Jan 23, 2012)

If you are looking to add it as some sort of substrate additive, as opposed to pest control, I think some of the oil absorbant products (ultrasorb?) are made out of granules of diatomaceous earth. I think it's commonly carried in autoparts stores, it's much lighter than safetsorb.

I think it's sometimes used in plant mixes for bonsai and such. Might still have trouble keeping it down, but it won't be as bad as the powdered stuff, although it may be harder to get a hold of.


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