# Laterite beneath Aquasoil and Power Sand??



## Akilia (Apr 8, 2006)

Hi there,

I have prepared my tank as per my sig.
I used a small pack of API laterite 1.5kg, 2L pack of ADA PowerSand M, and 9L ADA Aquasoil Amazonia.
The laterite was predominantly spread beneath the rear areas of the tank where the fastest-growing tall plants will be placed. The laterite and Powersand was used to ballast the RenaCor 25 W undergravel heater, which was suckered to the bottom.
Amazon soil was placed about 1/2 in deep at the front and 1 1/2 in at the back of the tank.
The soil was topped with 1in horticultural grit (washed).

I just read Walstad's Ecology of the Planted Aquarium, where she says she made a huge mistake using laterite with soil (Chapter VIII, E.1. Metal Toxicity). She argues that the acidity and humus content of the potting soil solubilized massive amounts of iron from the laterite causing iron toxicity to her plants. She describes root withering of floating plants, java fern withering, plants detacing from substrate etc.

Have I made a huge blunder??
How do I find out before I plant?

Regards,
Akilia


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## mrbelvedere138 (Jan 18, 2006)

I do not think Aquasoil has nearly the acidifying potential of rotting soil. Aquasoil is mostly pumice and peat, soil is mostly decaying plant matter. Soil is also ridiculously "richer" than Aquasoil, so I do not see a problem down the road. But of course, soil composition varies drastically in different areas, so keep that in mind.


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## plantbrain (Jan 23, 2004)

Do not add laterite.
You do not need it.

I can say this for any substrate actually.
I would add mulm etc, this will cycle the tank immediately.
You do not need any peat with ADA substrates but you can add a thin layer down prior.

It's not just Fe toxicity that can be an issue, but other oxidized metals as well. It's not acidity, it's reducing potential, the redox levels.

You can easily have an alkaline pH and very reducing conditions that release Cu, Fe, Al etc.

Reducing anaerobic substrates will over time tend to neutral conditions. the issue is the lack of O2 as an electron acceptor, pH does and can play some role, but not nearly as much as lack of O2.




Regards, 
Tom Barr


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## JKCoyne (May 1, 2006)

plantbrain said:


> It's not acidity, it's reducing potential, the redox levels.


Could you explain what this means (to someone with a very limited chemistry background)? Thanks.

-- J.K.


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## alphacat (Apr 26, 2006)

if something is oxidizing, it means there's a chemical reaction happening with oxygen (which is a fairly volatile molecule, i.e. fire won't start without it. There's a lot of stored energy in o2 molecules).

If you have excess iron, or any oxidizing metal, it will react with the oxygen and effectively burn it up.

PS: Redox is reduced oxygen in case you didn't know already. :nerd:


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