# Laterite and Walstad



## Skizhx (Oct 12, 2010)

So in Walstad's book she mentions that she experienced iron toxicity when she added laterite to her soil. 

She says she only added 1 cup of laterite... 

But does anyone happen to know how much soil she was adding the laterite to?

Has anyone else seen people experimenting with laterite and soil despite her experience?


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## SBS (Feb 26, 2013)

Well, I read around here she kind of said that the iron reacts with acids, causing iron toxicity in the roots. She mentions mixing peat and iron together is a no no for that reason. She used soil containing peat when she experienced that. And she also said that high organic waste eventually can cuase such acidic conditions in the soil, but every tank is unique about the balance.

But then again there's the mineralized topsoil method(there's a thread here by Aaron Talbot) which suggests adding iron rich clay to the topsoil(that should be free of peat) in 5-10% of the total amount, also dolomite to keep the soil from not going acidic. People have used it to very good effect too. It's just a different formula.

Many people have used iron rich substrate like laterite, akadama, flourite, etc..with great success so it's hardly just the iron the problem. And then iron in the substrate on another hand is good for the plants, because natural processes make it usable for plants in the roots, otherwise the water colum nutritients can render it useless(reacts with phosphorous for example). Clay and laterite and similar substrate materials have good caution exchange capacity(meaning trapping nutritients from the waste and water colum and keeping them for the plants to use later when they are ready). Clay to certain amount has good flocculant ability(makes the water clearer if any soil particles are released by replanting). And iron can neutralize the egg rotten smelly hydrogen sulfide experienced in more anaerobic soils, making it safer for both plants and fish.

So it's up to you which route to risk


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## Skizhx (Oct 12, 2010)

I'm aware of the role of humic acids and redox that lead to this apparent release of toxic amounts of iron...

I ask because I'm setting up some experimental jars with spare plants to test this. I'm not necessarily convinced by Diana's experience. She references a single personal case and provides very limited details. Not that I think she's making it up or don't trust her or anything... I just don't see sufficient evidence to make broad recommendations on.

Meanwhile I've seen some scattered mentions of people using top soil with organics in conjunction with laterite.

Mineralized soil is a bit of a different matter, as you've pointed out...

Just skeptical and wondered if anyone knew anything I didn't that could be helpful.


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## SBS (Feb 26, 2013)

> I'm aware of the role of humic acids and redox that lead to this apparent release of toxic amounts of iron...





> I'm not necessarily convinced by Diana's experience.


Then you know it all. In Diana's case that happened to be a big problem so she is not saying anything that you don't know already and it's not in contradiction of anything known. Then why doubt it? Then there are so many other factors that can prevent it in other tanks, like the type of water used, the type of maintenance, even how deep the layer of the substrate is, everything plays a role.
Diana is just playing it safe, that's all.


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## Skizhx (Oct 12, 2010)

I just want to know if anyone has any idea what the ratio of soil/laterite she used may have been, or if anyone knows of anyone that has mixed soil and laterite and could provide any details, or could at least give me some links to follow up on how their tank turned out. 

Unfortunately the scattered cases I've ran across don't provide much detail or follow-up of their tanks, so limited information there....


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