Suitable soils for the Walstad method

387161 Views 700 Replies 155 Participants Last post by dwalstad, 1 d ago

Michael

Discussion Starter · Jul 29, 2012 (Edited by Moderator)

"In general, aquatic plants seem to do well in a variety of soils-clays or loam soils with some organic matter. Indeed, I haven't been able to find any major or consistent difference in plant growth in various ordinary soils. . . . In most instances, substrate fertilization appeared to be either detrimental or not helpful. Best plant growth (under aquarium conditions) often appears to be not in the most fertile soil, but in the one that is the least toxic." Ecology of the Planted Aquarium, p 132.

So many people ask questions about which soils are suitable for use Walstad aquaria, it seemed time to start a thread on just that topic. Here is where we can share our results using different soil substrates.

First, some definitions. "Soil" has different meanings to different people. For our purposes, "soil" means any growing medium intended for terrestrial plants, but which we have adapted for use in the planted aquarium. "Topsoil" has a very specific meaning to soil scientists, horticulturists, and geologists. Often, what is labeled "topsoil" in a bag in your garden center bears no resemblance to natural topsoil as understood by science. Most natural topsoil is primarily minerals, with only a small percentage of organic matter. In our discussion, we should use the general term topsoil to refer to naturally occurring surface soil. When we are talking about a specific commercial product that has "topsoil" as part of its name, we should be sure that is understood.

Another term that needs definition is "organic". In this discussion, organic is used in the scientific or chemical sense; that is, material derived from living matter. This organic matter will be in various stages of decomposition. When I use the term "organic" I am not referring to the organic method of gardening, and I most definitely do not mean the undefined marketing hype used to sell so-called "natural" products.

And one last bit of clarification, when we talk about soil in this discussion, we are not referring commercial brands of aquarium substrates, like Flourite, Eco Complete, ADA Aquasoil, etc. Some of these products are very good, and may be useful in the Walstad method. Some are not.

I will start the discussion in the next post. But the only way that this thread can become really useful is if you post your knowledge, experience, and questions too!

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Michael

Discussion Starter · #581 · May 7, 2021

Welcome to APC!

This is a highly organic soil mix with added fertilizer, similar to the often used Miracle Grow. You can treat it in the same way. There are two basic approaches. The first is to use it straight from the bag, and be prepared to do large water changes in the first weeks or months. The second is to prepare the soil first, either by soak-and-drain or by mineralizing it. This will reduce the need for water changes. This soil may lower the pH of the water, but this is rarely a problem.

Good luck and show us your tank!

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gOOLY

· #582 · May 7, 2021

Michael said:
Welcome to APC!

[...]

Thank you! I'll definitely treat it and update you with some pics (and probably more questions). 😄

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gOOLY

· #583 · May 8, 2021

So, I've started the soak-and-drain process described both here and in the Aaron Talbot's topic on mineralization, but I've run into a problem.
Here you mentioned to add a substrate with a high CEC, but I'm having a hard time finding the ones you mentioned here. Would clay have the same effect? I've read in the other thread that
bentonite clay (which should be a type of montmorillonite clay) has a stronger CEC than normal clay, and I know where to buy it. Would that be ok? If not, do you know any alternatives or any other names to refer them to?

Also in that same thread, they mentioned to sprinkle some Dolomite and Muriate of Potash (whatever it is) on the glass, before adding the mineralized soil. How important is that? I could get the Dolomite but I have no idea on where to find the Potash thing.

mistergreen

· #584 · May 8, 2021

Potash is soluble potassium. I wouldn't overthink it or spend too much money on it. Any affordable clay is fine. The soil itself has high CEC. You can cap the soil with large grain sand or small gravel.

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Michael

Discussion Starter · #585 · May 8, 2021

Mistergreen is right, you can skip the potash without problems. Dolomite is a source of calcium and raises the pH slightly. It is useful if you have very soft water, but not necessary. After the tank is set up if you find the water lacks calcium, there are easy ways to fix it.

And don't worry much about the clay. Any type of clay is OK as long as it doesn't have any additive. If you can find some natural clay soil from a garden where no synthetic fertilizers or pesticides are used, that will work just as well.

The beauty of the Walstad method is that it is simple.

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johnwesley0

· #586 · Jul 10, 2021

Wonderful thread. I've come back to it now that I've been up all night reading EPA, a surprisingly fast read once you've spent some time on this forum.

Lately, I find that I keep coming back to the subject of clay. Diana's summer tubs are adorable and I find the look of a glass tank filled with clay pots aesthetically pleasing. But, I wonder at all that organic soil filling a 3" or 4" pot? Aren't you asking for anaerobic trouble? And, wouldn't some sort of clay, if merely for its cation-binding capacity, be the safer choice?

PlantFan

· #587 · Jul 10, 2021

johnwesley0 said:
Aren't you asking for anaerobic trouble?

Not after the roots get going.

maico996 said:
You'll need as many plants as you can get when you start the tank. When you think you have enough...add more! Some will die off (that's just the way it is) and the rest will do their thing. You want lots of rooted plants to help aerate the soil. And some floaters too to help absorb excess nutrients. If you don't have a lot of plants to start with you're inviting algae to take hold in your tank, along with the possibility of anaerobic conditions developing in your soil which you want to avoid.

I like clay though.

johnwesley0

· #588 · Jul 10, 2021

PlantFan said:
Not after the roots get going.

I like clay though.

That makes sense in conjunction with the bottom of an entire tank. But, a single pot often has room for only one plant. If that plant happens to be a slow-growing anubias, wouldn't it still be asking for trouble? Or, what if it's just a bulb? No chance for roots to catch up there.

PlantFan

· #589 · Jul 10, 2021

Maybe we shouldn't pot Anubias and bulbs. I haven't given it much thought. It was a revelation to me that roots aerate soil.

mistergreen

· #590 · Jul 10, 2021

Anubias and ferns are epiphytes. They do better glued or tied to rocks & wood.

johnwesley0

· #591 · Jul 10, 2021

mistergreen said:
Anubias and ferns are epiphytes. They do better glued or tied to rocks & wood.

Funny. I've owned the same two anubias for nearly six years and I've never had the slightest desire to glue them or tie them down to anything. And now that I've said that, it sounds kind of creepy.

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mistergreen

· #592 · Jul 10, 2021

If you have little anubias, it's good to glue them to something so they don't float away. In nature, you find them attached to the side of rocks by streams and such.

johnwesley0

· #593 · Jul 11, 2021

mistergreen said:
If you have little anubias, it's good to glue them to something so they don't float away. In nature, you find them attached to the side of rocks by streams and such.

I don't really remember what kept them from floating in the early days. I think because I only saw them from the top down that it never really bothered me that due to their rhizome they were mostly untethered from my very shallow substrate. But, in their mature state they clearly have intricate root systems. They thrive on mulm, so that's an important niche in my bowl I'm not going to disturb. But, I could definitely see starting a new one in a pot.

jatcar95

· #594 · Jul 13, 2021

johnwesley0 said:
But, I wonder at all that organic soil filling a 3" or 4" pot? Aren't you asking for anaerobic trouble? And, wouldn't some sort of clay, if merely for its cation-binding capacity, be the safer choice?

From Ms. Walstad's Small Scale Guppy Breeding article: "For potting plants, I only use a clay garden soil. (Potting and organic soils can become severely anaerobic when confined in a pot.) I cover the soil with a little aquarium gravel." Article is linked on this page: Planted Aquariums

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clarke77

· #595 · Jul 15, 2021 (Edited)

Hello! First post. My daughter and I have been reading Ms. Walstad's book, lurking on this forum, and watching a bunch of YouTube videos and we think we're about ready to take the plunge into our first planted tank!

Of course, we're stuck on the question of what soil to use. There is a garden center nearby that has a number of options available, and they provide detailed descriptions on their website. At this point, I think the best option is one they call "Potting Mix"...it clocks in at around 20% organic matter, composed of "Sandy Loam, 5/16" Horticulture Lava, Coarse Sand, Organic Diestel Compost, Organic Garden Compost, 1/4"-Fir Bark, Ligna Peat, and Organic Feather Meal".

Can someone take a look this (their provided soil analysis) and let me know if this would be a good choice:

https://store.lyngsogarden.com/inet/storefront/getpdf.php?recid=278

Thank you!

dwalstad

· #596 · Jul 16, 2021

No guarantees, but I don't see why it wouldn't work. I assume that this soil is being sold by a reliable garden center to grow houseplants. The fact that it is only 20% organic matter will lessen its tendency to go anaerobic. (Some potting soils are over 60% organic matter.)

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TheGarbagePile

· #597 · Aug 15, 2021

3

I run two 10 gallon tanks and I have had some great successes using regular miracle grow potting soil ( I did not mineralize). A small bit of osmocote ,and a cap of about 1-2 inches of fluorite sand or regular sand. I have budget hygger lights and do not inject Co2. I do have aquaclear HOB filters on both. The tanks are over one year old. I can see through the underside of the tanks and I'm pretty sure the soil has nearly fully decomposed to humus. The tank capped with fluorite has all of my red plants in it and they are spectacular. I do have some deeply rooted plants in both tanks along with a small army of Malaysian trumpets so anaerobic areas have never been an issue in either tank. I just also recently started a 6 gallon long using the same method. The shorter height tank has had explosive results. I am also using a fluval 3.0 on the 6 gallon so the better light helps. The tank has been active for about 2 months now. I dont think theres to much need to overcomplicate the substrate preparation process.

Plant Light Leaf Botany Wood

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Michael

Discussion Starter · #598 · Aug 15, 2021

Beautiful tanks!

dwalstad

· #599 · Aug 17, 2021

Reassuring pictures of your tanks. That Red Tiger Lotus is gorgeous!

I welcome your idea of keeping it simple. Thanks for posting.

PlentyCoup

· #600 · Aug 25, 2021

Been slowly working my way through this dicusssion i think im on page 13 now so if this question has already been asked i apologize.
Ive seen the comments about people using compost mixed with bonsai soil that i thankfully have on hand for my bonsai plants.

My question is thag i currently have 2 yards of compost left in my driveway that came from the city and is made from all the yardwaste collected im my county.
Its been furter decomposing under all the heat weve had (got it delivered in june)

Would it be safe to use since i dont know the orgin what makes up the compost?
I know chemicals can hang around some have long half lifes and thats not even inculding any diseased plant matter (which should never be put in homemade compost).

Now i have never had a issue in the ten+ years ive been putting the compost on my garden beds, but i have also never used it for a aquarium.
Any insight would be gteat,.

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