# Aquasoil vs. Capped Soil



## Mattypants (Mar 2, 2019)

I've been planning on doing a first Walstad 15G using potting soil and a fine gravel cap, but wondering if ADA Aquasoil with no cap is a viable option as well? Would this still be considered a Walstad setup? Does Aquasoil have the ability the replenish it's nutrients over time in the same way that soil does?


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## Maryland Guppy (Dec 6, 2014)

Either will eventually become depleted of everything.


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## Mattypants (Mar 2, 2019)

Maryland Guppy said:


> Either will eventually become depleted of everything.


So the surplus food doesn't break down fast enough to keep up with the load whichever route you go unless you add fertilizer? Is the long-term no-fert solution to rotate between water column feeding plants and substrate feeding?


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## AquaBryan (Apr 21, 2018)

Hi,

Walstad method is named after Diana Walstad, who founded her own method of balancing a dirted tanks. Key word: dirted tanks. Her main choice of substrate is soil(ie garden or potting), this being a big part of the reason it’s her method. So you using an aqua soil will not consider it a walstad method as it won’t be her method. It’ll just be a filterless tank with aqua soil. I’m not saying it won’t work, it just won’t technically be a walstad tank.

I don’t believe aqua soil will replenish its nutrients, since as it ages, it tends to break down to pieces.


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## AquaAurora (Jul 10, 2013)

I recently set up 4 dirted tanks (was suppose to be 2 >.> I over ordered plants). I used miracle grow organic potting mix, 2 tanks capped with black diamond 'sand' (coal slag), the other 2 with gravel. I will say gravel is harder to plant in and makes more mess with letting soil loose during planting. But gravel will let mulm move down into the soil again over time. Can't say that it will replenish the soil so you never have to add otehr ferts (root tab or liquid), would image that varies tank to tank with stocking, plant choice, and feeding.


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## Mattypants (Mar 2, 2019)

AquaBryan said:


> Hi,
> 
> Walstad method is named after Diana Walstad, who founded her own method of balancing a dirted tanks. Key word: dirted tanks. Her main choice of substrate is soil(ie garden or potting), this being a big part of the reason it’s her method. So you using an aqua soil will not consider it a walstad method as it won’t be her method. It’ll just be a filterless tank with aqua soil. I’m not saying it won’t work, it just won’t technically be a walstad tank.
> 
> I don’t believe aqua soil will replenish its nutrients, since as it ages, it tends to break down to pieces.


I agree that I couldn't call it a Walstad tank since the method is specific to her setup.

Not sure I understand how the fact that the Aquasoil breaking into smaller particles would affect it's ability to replenish itself from mulm.


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## OVT (Nov 29, 2011)

A quick primer on CEC Cations and Cation Exchange Capacity | Fact Sheets | soilquality.org.au

One thing to keep in mind is the studies focus on terrestrial soils, not submerged in water. This is where ADA were the innovators to bridge the two medias, but even they recommend replacing AS every 2 years, if not sooner. Another thing to keep in mind that AS does not just break into smaller particles, it completely breaks into dust /mud over time (2 - 5 years).

The rate at which AS, end even more so soil, leaches nutrients, including organics, into the water column is hard to control. In both cases, you will still need to suplement with substrate / water column fertilization, sooner or later.

Another trademark of Walstad tanks is the density and viriety of plants and the natural / wild look, including the algae, the idea being selfsustaining, for a while, over the looks / aquascaping.

Depending on your goals, either soil, AS, or neither might be suitable for you needs.


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## Mattypants (Mar 2, 2019)

OVT said:


> A quick primer on CEC Cations and Cation Exchange Capacity | Fact Sheets | soilquality.org.au
> 
> One thing to keep in mind is the studies focus on terrestrial soils, not submerged in water. This is where ADA were the innovators to bridge the two medias, but even they recommend replacing AS every 2 years, if not sooner. Another thing to keep in mind that AS does not just break into smaller particles, it completely breaks into dust /mud over time (2 - 5 years).
> 
> ...


Thanks for the clear response. Makes sense that the Walstad method can't really be compared to AS, since the goal is a bit different.

I've noticed that a lot of seemingly experienced aquascapers use a layer of sand or gravel under their AS - are they attempting to build more bacteria in the media? Curious as to why they just don't use more AS... Cost?


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## OVT (Nov 29, 2011)

You are very welcome.

I have actually noticed the opposite trend: people capping AS. I did that in one of my tanks in hopes of containing the dust from AS (partially successful). My guess for doing it the other way around would be to save on cost. A more common approach is to use lava rock under top substrate to build up hills and to save, again, on cost.

If the sand bed is deep (4"++) then the goal might be to create conditions for anaerobic bacteria and that approach is more common in salt water tanks (search on "deep sand bed").

Otherwise, there are planty of room for bacteria in planted tanks.


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