# When outdoor soils are the wrong choice



## davemonkey (Mar 29, 2008)

This topic had been asked about many times in many threads, but I don't think anyone has ever really dedicated a thread to it...at least I have not seen one.

Not only in the world of NPT, but also in Dutch and in other tank-keeping styles/methods hobbyists often choose to use regular soil from outdoors. I have a couple of times, but one time it ended up being a real pain. This was in my 125. I think I had mentioned it, but never really discussed it, so...I'm providing these thoughts to help keep others from making my mistake:

...Here is what I did wrong. I found a local clay-loam and decided to use it due to its nutrient richness and high cation-exchange-capacity (CEC). I "mineralized" it per that thread on mineralizing topsoil, even though I didn't need to (outdoor soils are already "mineralized"...having been wet/dried thousands of times in as many years). 

Anyway, I forgot about flocculation. This particular soil in my area doesn't flocculate well...meaning, in water, the particles tend to disperse. I could have chosen a heavier clay soil...but I preferred "loam" because it was less dense...easier for plant roots to get through.

What I ended up with was tiny particles floating about my tank...with no way to filter them out. Even with 100% water changes or temporary canister filter use...the water would be crystal clear for a few hours and then get the particles floating about again.

From my limited experience and from reading other people's threads...I have noticed that the soils high in organic matter (those purchased at garden stores) tend to have less problems than mineral soils (from the yard). I am also starting to think that it doesn't matter how nutrient rich a soil is. I believe (and please feel free to correct me) the majority of available nutrients in any soil are going to be released in a matter of weeks (at least as far as N ), and after that, all nutrients that plants are getting are from fish food, waste, and decomposing OM...and added ferts.

What I SHOULD have done was: 1) Either add a flocculating element to the soil, such as dolomitic limestone (I think AaronT talks about this in his "mineralizing topsoil" thread)... OR 2) just gone with "MiracleGro Organic Choice" like I did with other NPT's... OR 3) used ADA Aquasoil (Amazonia).

If I do it again; for low-tech I'll use the "MiracleGro Organic Choice" and mineralize it per that thread, and cap it with something pretty. For high-tech I'll stick with the ADA substrate. It releases lots of nutrient load at first, but after it settles down, it is the quickest route to a stable substrate.

On my daughter's "Rita's Princess Tank" thread, I just re-did hers and we used "topsoil" from a garden center. It's anything BUT topsoil...looks basically like composted peat and other vegetation...very fiber-heavy and zero mineral soil. We put that in sloping from 0.5" in front to 2" in back and capped with regular gravel. Total depth is 1.5" at front and 4" at back. No problems at all with her tank now except when I try to fertilize it (gets algae on the glass when I add ferts...so maybe I shouldn't do that  ).

Anyway, these are just some thoughts I felt would be useful for others who are considering a soil layer in their planted tanks. 

-Dave


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## davemonkey (Mar 29, 2008)

Oh, and just to clarify...I did not mention the Aquasoil (ADA's Amazonia, etc... ) except for high-tech. I actually beleive that the ADA substrates are PERFECT for low-tech tanks. All you have to do is get through those first 3-4 weeks of nutrient release and water changes. The reason I mention only doing ot for high-tech is because most people looking to low-tech also have the issue of sticking within a budget. But, if budget is out of the picture...I'd go with the Amazonia every time for every scenario because it's already in a state that takes our "home-made" versions 6 months to get to.


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## HeyPK (Jan 23, 2004)

I am curious about these tiny particles. Do they come from the soil? How do they get into the water, if you have the soil capped with gravel? Do they not settle out? Clay particles are so small that they can form a suspension that persists and makes the water cloudy for a long time. Is that what these particles are? Do these particles persist in a tank that has a good growth of plants, or are they only a problem before the plants get established?


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## davemonkey (Mar 29, 2008)

Good question, Paul. These were particles that were tiny, yet visible to the naked eye. If I had the powerheads off, they would settle eventually (after 2 days or longer), but any water movement stirred them up again. I had siphoned the the substrate surface (which was used Amazonia mixed with used Eco-complete), and performed near-100% water changes almost weekly...and the problem persisted from set-up through the end of the tank's life when it was extremely heavily planted and well-aged. (The tank has since been sold. )

So, do you think it was OM instead of soil particles? I figured it was soil creeping its way up through the top layer. At one point I thought it was the driftwod, but after several months of being in the tank the wood had a smooth surface with no signs of breaking down.


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## HeyPK (Jan 23, 2004)

Yes. If they were visible to the eye, and mineral, they should sink like stones. It must be mulm debris that gets stirred up. Now, it is interesting why you would get this organic debris when you have natural topsoils , but not when you have all organic potting soils. This debris might be the indigestible remains of algae that has been through the digestive tracts of snails, fish and other critters. It may be that the all organic potting soils release tannins or who-knows-what that prevents the growth of algae. (Just speculating!)

I often have mulm build up, but I have never seen particles so fine that they didn't settle out in an hour or so when the water was still. I wonder if you had a case of Cavan's dreaded grey slime. I am not sure what he had; it may have been some kind of alga , but it tended to form strings of particles that could be easily be broken up


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## Michael (Jul 20, 2010)

Davemonkey, thanks for starting this thread.

The other cause of problems with natural soils is colloidal clays. These are clay particles that are so small that they never settle out of the water--Brownian motion is enough to keep them suspended indefinitely. They are also too small to be removed by any common aquarium filter media. Fortunately, a simple jar test will reveal their presence. This is the reason why I can't use the Blackland Prairie soil from my Dallas backyard.

Again, it seems that MGOC is not an ideal soil for aquaria, but it is a consistent, nationally available product. Its drawbacks can be solved by various simple, if messy and time consuming, methods.

As Davemonkey points out, the cheap generic bagged "topsoil" often recommended can have problems. There is no real control over the ingredients of such "topsoil" and you may get soil, or some mix of things that might become soil someday.

Just a note, I believe the flocculating ingredient in AaronT's recipe for MTS is the pottery clay, not the dolomite.


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## davemonkey (Mar 29, 2008)

Michael said:


> Davemonkey, thanks for starting this thread.
> 
> The other cause of problems with natural soils is colloidal clays. These are clay particles that are so small that they never settle out of the water--Brownian motion is enough to keep them suspended indefinitely. They are also too small to be removed by any common aquarium filter media. Fortunately, a simple jar test will reveal their presence. This is the reason why I can't use the Blackland Prairie soil from my Dallas backyard...


Maybe that was my problem then. I think the soils here are similar to the blackland prairies...the major component here is "Beaumont clay" which can be likended to "Houston Black".



Michael said:


> Just a note, I believe the flocculating ingredient in AaronT's recipe for MTS is the pottery clay, not the dolomite.


Ah, yes...thank you for catching that!


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## Michael (Jul 20, 2010)

Yep, that's the sticky stuff I have--Houston Black.


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