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How-To: Mineralized Soil Substrate, by Aaron Talbot

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#1 · (Edited by Moderator)
How-To: Mineralized Soil Substrate


Over the years dedicated aquatic plant hobbyists have developed many different methods to maintain vibrant freshwater flora. After having tried almost all of the popular fertilization techniques, I have finally found one that produces consistently healthy aquatic plants. That fertilization method imparts essential nutrients by using mineralized topsoil as a substrate.

When I joined the Greater Washington Aquatic Plant Association about four years ago, I attended my first official meeting at the home of Sean Murphy. Sean is a Fisheries Biologist by trade and has been employing mineralized soil in his planted aquariums for nearly two decades now. He developed a "recipe" for the soil substrate during his collegiate studies of wetlands soils. It is his recipe that I have recently begun using with great success.

Using topsoil or potting soil as a substrate is not a new idea. Aquarists have been using this method to grow healthy aquatic plants for decades. However, this method does seem to pose some problems, namely algae outbreaks resulting from light intensity that is too strong. This is especially true when you first set up your aquarium with this type of substrate. The algae likely results from the excess nutrients that decomposing organic materials release in the soil. The decomposing organic materials are not bio-available to the aquatic plants. As the tank matures, the algae dissipate slowly as the organics in the soil finish breaking down.

Mineralizing the soil beforehand helps to speed the breakdown of organic materials in the soil. In turn the mineralized soil will help shorten the initial algae outbreak period that many aquarists experience when using a soil substrate. Soil mineralization occurs from exposing bacteria, enzymes and other soil microbes to oxygen in a moist environment. The microbes break down the organic materials in the soil into bio-available minerals. As an added bonus these new bio-available forms of nutrients are generally only available to plants and not to algae.

There are a few other components to the mineralized soil recipe. Clay provides a source of iron. The clay also serves to bind with the soil as a flocculating agent. When plants are uprooted or disturbed, the added clay will help the soil to settle back to the bottom of the tank. Adding Dolomite to the base of the substrate will provide plants with the necessary calcium and magnesium they need for healthy growth. The calcium and magnesium in the dolomite will also help to keep the soil from becoming too acidic. Lastly, add soluble potash for an initial potassium source.

It is still possible to use pressurized CO2 and high lighting with this method of fertilization. I have setup four tanks using this method and all of them have been high-tech setups using CO2 and high lighting. I rarely ever have to dose any supplements save for the occasional dose of potassium. Use caution when dosing and dose very little amounts at a time.

I've composed a list of materials and step-by-step instructions for those readers who would like to try the mineralized soil substrate method.

Materials Needed

Cheap topsoil
Pottery clay
Dolomite
Muriate of potash
Fine gravel or coarse sand
• Large container for soaking soil
• Screen made from scrap wood and chicken wire
• Nylon screening material
• Large plastic tarp

Step 1 - Purchase and Rinse the Topsoil

Open the bag of topsoil and distribute in the container of your choice for soaking purposes. I use large Rubbermaid containers that are readily available from any mega-mart. You will want to use cheap topsoil and not potting soil. Potting soil has additives to avoid such as fertilizers, vermiculite and peat moss.
Fill the tub with water so the water level is a few inches above the top of the soil. I like to stir it around a bit to help break up any big clumps and evenly distribute the water. Let this soak for a day or two. Come back and slowly dump the water off of the top. Now add in more water so the soil is well covered. This water changing process helps to "rinse" the soil of any possible fertilizers or other harmful water soluble chemicals.

Step 2 - Allow the Topsoil to Dry

Pour the excess water out of the container as you did when changing the water. Lay out the large plastic tarp, preferably in direct sunlight. Dump out the muddy soil and spread it relatively thin over the tarp. Allow the soil to dry completely. This can take a day or two and depends greatly on how warm the temperature is where you are drying the soil. This part of the process could be done indoors. Though due to its messy nature, I suggest doing it outdoors if possible. When the soil is completely dry, add it back into the soaking container.
The drying process is the part that allows the microbes in the soil to begin mineralizing the nutrients. Exposing it to air oxygenates the soil.

Step 3 - Repeat the Rinsing and Drying Cycles

Repeat steps 1 and 2 three to four times. Repeating the steps is necessary to further mineralize the soil and remove any lingering fertilizers. The soil mineralizes the most during the time while it is still moist and exposed to air on the large tarp. By soaking it over again we reintroduce the needed moisture for this process to take place. When the soil is near fully mineralized it will have a very grainy texture. Another way to tell that the soil is ready is by smell. There will be virtually no smell coming from the soil once it is mineralized.


Mineralized Topsoil

Step 4 (optional) - Sift the Soil to Remove Debris

Screening the soil can help to remove any large organic materials that the short mineralization process employed thus far cannot remove. I have setup tanks where I skipped Step 4 and others where I used it. I have found that adding this step to the process helps to further eliminate algae issues after a tank is newly setup.
You can use a wooden frame with chicken wire stapled to four sides. Then place nylon screening material overtop. Place a few handfuls of soil on top and gently push the soil across the surface of the screen. Make sure to put a container underneath to catch the sifted soil. Below is a picture of the sticks, leaves and stones that can be removed during this step. The resulting sifted soil will feel like airy sand.


Screening Setup

Step 5 - Add the Clay

Now that you have a mineralized soil to use as the substrate, you will want to add in the aforementioned clay. Estimate how much clay you will need so that the resulting mixture of soil and clay is about 5% to 10% clay. If you prefer measurements I use about ¼ of a pound of clay per square foot of tank bottom.
To add the clay you soak it in a container of water to help emulsify it and make it easier to incorporate into the soil. A second option to add clay is to dry the clay in the open air and then crush it into a powder and add it to the soil. In either case you will want to eventually add enough water to the mixture to form a nice runny mud.


Mineralized Soil Mud with Clay Added

Step 6 (optional) - Create an Aesthetic Border

Now comes the fun part of setting up the aquarium. Add the gravel of your choice just along the front and side edges of the aquarium bottom. Wet it just enough that it holds a slope and press it up against the sides. Doing this step ensures that we will not see the different layers of substrate when viewing the tank from the front and sides. In this instance I have chosen to use 3M Colorquartz T-Grade Black Sand as a substrate top layer. I prefer this coarse sand for many reasons. It is very dense and holds a slope for a long period of time. The finer granules also allow for easy planting.


Sand Border

Step 7 - Add the Dolomite and Muriate of Potash

Sprinkle a light dusting of both the dolomite and muriate of potash on the bottom glass of the tank. The bottom of the glass should still be somewhat visible.


Sprinkling of Dolomite and Potash

Step 8 - Add the Mineralized Mud

Fill in the borders you've created with the runny mud mixture of mineralized soil and clay. This layer should be anywhere from ½" to 1" deep.


Mineralized Mud Added

Step 9 - Top With Gravel

Cover the mud with more of the same border gravel from step 6. If you skipped step 6 then simply cover over the mud with the gravel of your choice. Cover the mud by about 1" in the front to 2" in the back of the tank to create a nice sloping substrate effect.


Gravel Top Layer Added

Step 10 - Slowly Fill the Aquarium and Begin Planting

Begin planting and filling the aquarium as you would any other planted aquarium. Use caution when filling the tank with water. Go slowly to avoid disturbing the substrate and uncovering the soil.

The End Product

I hope this has inspired you to try something new. I know I had wanted to try mineralized soil for some time after seeing Sean's beautiful aquariums. I finally got up the courage to set up a small 20 gallon tank last year and now I'm hooked. With a little patience and trial and error, I think you'll be pleased with the results.


My ADA 90-P aquarium with a mineralized soil substrate


My AGA 75 gallon aquarium with a mineralized soil substrate
 
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#188 ·
No, that's what's known as a soilless mix. It's added to topsoil to enrich it for terrestrial plants. You want good old dirt without organics such as manure and forest humus and all of those other additives. DianaK. made a great post a few pages back about what type of soil is appropriate to use.
 
#186 ·
muriate of potash is used in agriculture as a fertilizer--Head to the nearest farm/feed supply store. I was given a pound for free (still made the proprietor take some cash on principle) after telling him what I was using it for. This is sold in mass quantities. You certainly are unlikely to need 50-100-1000 lbs unless you want to use it on your fields as well(!)
If you want dolomite without worrying about other additives, it is sold in crushable pill form (saves having to buy large quantities) at any health food store, and I believe that I saw it in the vitamin aisle at Wallyworld. Cheap, too.

Kudos to Aaron T for publicizing this method in such detail. No matter how long you remain in this hobby, you can always find something you haven't tried, haven't kept, or haven't bred yet. Now I have a legitimate excuse for playing with mud beyond growing this season's veggies.
 
#190 ·
Thanks a lot for that link Aaron. Just curious since its been a long while since you originally posted this method what have you noticed about your long term need for dosing? Have you ever added anything other than K to tanks set up like this? and in what time range have you noticed that you needed to start adding K, and in what amounts?
 
#194 ·
K has still the only thing I've ever needed to dose. I've had tanks running about 3 years now before I've had to tear them down (not for needing to redo the substrate, but for moving reasons). I usually need to start adding K about 4-6 months after the initial setup. I dose about 1.0 ppm / week or less. It doesn't take much.
 
#191 ·
Hello all,

I recently got a used, but nearly new, 29 gal biocube from a friend of mine for free, so I guess I am now going to start a planted aquarium. So that also means I am a noob to the hobby.

I am considering doing this mineralized soil approach, but I have some ideas for a slightly different approach. I guess it would be appropriate to document methodology here in order to get input from others who have been experimenting for years, assuming this is OK with Aaron?

A little info on me. My formal education includes a BS degree in soil science and hydrology, and nearly a second BS in applied plant biology. I would be happy to answer any of the more technical questions people might have with regard soil based substrates (per the topic).
 
#192 ·
Hi Kiril, great minds think alike, lol since I’ve also been pondering on a way to make a mineral enriched substrate in a more simple way and with less effort than the one illustrated by Aaron, and with less plagues with nitrogen and other macros leaching from the El Natural method during the early phase of setup. I look forward to see your ideas and different approach when you start to post. Maybe you can start a journal on it.
 
#195 ·
Hi Kiril, great minds think alike, lol since I've also been pondering on a way to make a mineral enriched substrate in a more simple way and with less effort than the one illustrated by Aaron, and with less plagues with nitrogen and other macros leaching from the El Natural method during the early phase of setup. I look forward to see your ideas and different approach when you start to post. Maybe you can start a journal on it.
I may start a journal on the process. Basically I am looking at building a soil medium that will hopefully work with normal tap water in my area and provide a long term source of nutrients for the specific type of plants/tank environment desired. I will not be using generic top soil in order to avoid the negative impacts associated with decomposing organic matter and to eliminate the wet/dry mineralization steps. If everything works the way I envision it, the different components of the substrate can be prepped, mixed, and used almost immediately.
 
#199 ·
I CANNOT RECOMMEND MINERALIZED TOPSOIL ENOUGH!

I get way thicker growth, way less algae, and more species are doing well than in my "EI" tank.

If you have an empty tank, get some right away. (mind you it takes a month to prepare) but it gives cheap easy results! Bear in mind that there is no way I can profit from endorsing this stuff.
 
#200 ·
hey aaron,
great post! very useful! going to be using it soon! i would just like to ask some questions please!

at step 6 when putting the gravel over the mud wouldnt some of the gravel sink into the mud? thus causing a mixture thing?

and as for adding the clay? is there any sort of specific clay you must use or any?

thanks
 
#203 ·
I used pottery clay, the red stuff. I am not sure if the other clays have lotsa iron, but I can attest that I have great growth and have never dosed iron in my mineralized topsoil tank. Therefore, one can conclude that red clay has iron. You could probably find some at an art supply store, if there is one in your area.

Adding sand overtop is fine. I don't think it matters what kind, but allegedly playsand is more lightweight than other sand so it's less likely to sink. I didn't have enough sand, so some of the soil was exposed to open water. All that happened was the tank was cloudy for a few weeks. A couple water changes and filter cleanings and it is all good.
 
#204 ·
Hey aaronT,

I am going to be trying this method with my 90 gallon tank, which I am going to be redoing now in the 5 week holidays we have here in South Africa during the Soccer World Cup. I am too lazy to go and look around for proper topsoils so i just dug some out of my garden and have started soaking it today! I will continue to post updates over the days ( weeks ) and will post pictures of the final product, so stay tuned :)

The Garden soil


Starting to rinse
 
#205 · (Edited)
Ok, i walked my dog just now to the local art/ stationary supplies shop and i found this stuff called terracotta? It was in some weird language so i couldn't find out if it had a high iron content, it say moulding clay/paste at the back, heres a pic of it -

Funky clay


should i give it a shot its only R29 which is about $2 or $3
 
#210 ·
Hello! I live in georgia and was wondering if I can use the red Georgia clay that is so prevalent in this area? This is the kind of clay that makes our rivers turn red when it rains and will stain your clothes orange.

Can I use only Georgia clay since I wouldn't be using the type of clay you use for pottery? I would just be digging it up from the yard. Could I get away with only a 1/4 inch layer of pure ga clay with 2 inches of fluorite over that?

Also, assuming i can't use Georgia clay place of garden center topsoil, can I use silt from a pond? We have a cabin on a small lake that's being filled in with silt from erosion upstream (construction). There is a lot organic matter in this silt since the lake has basically become a bog. Would using this organic rich silt be preferable? It doesn't appear to be clay-based because it's dark brown and clay isn't common at our cabin.

The silt seems to be extremely low in nutrients and minerals, and seems to be primarily organic matter because sphagnum moss and pitcher plants grow well in it, and sphagnum moss and pitcher plants can not tolerate nutrients or minerals. I'm unclear as to whether it's desirable to start with soil that's mostly organic matter so that you'll end up with more mineralized media in the end, as opposed to substrate that is mostly inorganic to start with. This stuff is thick silty muck.
 
#213 ·
Hello! I live in georgia and was wondering if I can use the red Georgia clay that is so prevalent in this area? This is the kind of clay that makes our rivers turn red when it rains and will stain your clothes orange.

Can I use only Georgia clay since I wouldn't be using the type of clay you use for pottery? I would just be digging it up from the yard. Could I get away with only a 1/4 inch layer of pure ga clay with 2 inches of fluorite over that?
I tried using the type of red clay we have here in FL and it just turned into an orange mess. Maybe I wasn't doing something right, but when I mixed it with water it all pretty much stayed suspended in the water until you let sit for awhile then the slightest movement of the water would stir it all up again. It doesn't seem to be the type of clay the the pottery stuff is more silty dirt clay. But then again thats the FL clay i used from my yard.

You could always go through the process then test a small amount out and see what happens.
 
#216 ·
I'm sure it's the same or almost the same stuff. I was thinking of just using a small amount, like a quarter of an inch covered by two inches of fluorite.

How many inches of substrate did you top it with, and how deep was your layer or clay?
I wouldn't use just clay as the soil layer. The mineralized soil layer should be about 90% soil and 10% clay. Using too much of any type of clay will result in a cloudy mess.
 
#215 ·
hi guys just a quick question, please respond quickly. I bought some $6 clay for my 16 gallon fish tank which i am going to be converting into a mineralized topsoil tank with plants. here are some pics of the clay please tell me if its suitable, because it doesnt mention ingredients on the back( high iron content ) and i put it in the oven to bake abit as i am going to crush it then put it in. thanks alot

package
http://i672.photobucket.com/albums/vv90/cheddar254/29062010235.jpg

actual clay
http://i672.photobucket.com/albums/vv90/cheddar254/29062010236.jpg
 
#217 ·
This article: http://amania.110mb.com/Chapters/Tech/sub-aquasoils_en.html

States not to use KCI (muritate of potash) in the soil as it kills bacteria.

Not saying that's the case as there are many articles and much info on the web that often conflicts, but the article is quite in depth and I thought it worthy of discussion.

What forms of potassium are available to plants via soil? K+ is not, correct?
 
#222 ·
I've seen and read that article before and found it quite interesting. That said, I don't think it's referenced well, making the task of checking the primary sources difficult to say the least. If you had read the article more carefully, you will see that he states that KCl will kill bacteria when used at a quantity of 5-10%. The amount of KCl used in mineralized soil is probably much lower than that overall. If you have it available, i'm sure that K2SO4 could also be used, but since KCl is more readily available, that is what is suggested.

Finally, K+ is the only oxidation state of potassium readily available and stable under standard (and aquarium) conditions...
 
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