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Needing Advice On 40Gallon Dirted Aquarium

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I don't wish to spend upwards of $173 on branded Aquarium Soil for my 40gal, I am wishing to do a dirted tank. This will be my first planted tank and I've heard newbies shouldn't do it but I'm doing one anyways! Any advice given for this would be appreciated as I am still in the midst of doing my own research.


(Sorry if I am posted in the wrong forum, I just joined)
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I have a dirted 20 long. I bought a bag of topsoil and a bag of play sand from Ace Hardware, put ~1" of topsoil on the bottom and another ~1" of play sand on top of the soil. Total cost: about $5. It's been set up for about 3 years, plants are doing great, no issues.
 

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"Dirted tanks" can mean a lot of different things.

1. 'Potting mix' tanks - these use some (about an inch or so?) of potting mix under an inch or two of inert cap (inert = sand/gravel/fired clay substrate). I believe this is how the Walstead Method goes. The idea is that the potting mix provides a soft rooting medium, plant nutrients (from the slow decay of the mix components), and a slight CO2 boost (also from decay - nothing like CO2 injection levels, but more than zero). The organic matter of the potting mix has a very high CEC (cation exchange capacity) that may 'grab' nutrients from the water column and hold them where roots can get to them. Currently a very popular method.

2. 'Backyard soil' tanks (this is what I run) - You dig up some soil from your backyard, away from house boundaries (so that you don't get things like paint flakes or soaps from siding/window washing, etc), away from any place pesticides have been used (avoid under-lawn soils that have had weed-n-feed, etc) in the last few years, and away from anywhere that's been heavily fertilized recently. The soil needs sifting (through window-screen type material - I used a wire kitchen sieve), you want to pick out any worms, bugs, sticks, root masses, or rocks that you find in there. Different folks may add in different mixins - a cup of red clay as an iron source, vermiculite to make the soil mix "softer", peat/compost as organic matter, etc. All optional, all with pros/cons. Then, about an inch along the tank bottom with at least an inch of inert cap over it.

3. 'Mineralized topsoil' tanks are all the current rage. You buy very cheap topsoil from a garden center. This should basically be the same sort of stuff as you dig up in your backyard, a mineral mix of very fine sand, silt, and possibly some clay particles (that's what dirt/soil is, as opposed to a potting mix that is all carbon-based ingredients like peat, compost, leaf mold, etc), all depending on the source. You can use this stuff directly as for backyard soil (I would sift it), or 'mineralize' it by doing a "moisten - spread in thin layer - dry in sun" cycle several times. You'll find lots of posts about mineralizing topsoil and its supposed benefits. Currently a very popular method.


Then there are a lot of 'mixin' ingredients that can be used with any of these kinds of 'dirt'.

1. Clay - usually red clay, meant to provide a very high CEC, soft, high iron material. Pros - holds nutrients well, provides good root contact. Cons - clay particles are very small and can stay in solution in water for days. So every time you uproot a plant, a bit of clay will come with it, and cloud your water for hours. Can be mitigated by lots of water changes after a large rescape session or filtering with a fine material to catch the clay particles (even filter floss helps a lot). Some people mix it in powdered form in dirt at tank setup, some people make root tabs (clay mixed with Osmocote+ fert or other dry fert mix), air dry them, and shove them to the bottom of the substrate after planting). Used to be all the rage in the old days, Dupla made a ton of money selling laterite (a very high-iron clay mixin) back in the day.

2. Earthworm castings - an organic fertilizer made of earthworm poop. If the worms were grown in dirt (as opposed to an organic potting mix), then there will be a small mineral component here too. I don't know much about this, it's pretty pricy IMO, but I expect it is good stuff.

3. Osmocote+ Indoor/Outdoor fertilizer pellets. Lots of people use these, you scatter a bit on the tank floor under the dirt, it's supposed to release nutrients over 2-4 months in the aquarium, depending on temperature. People use these under gravel substrates too. Don't overdo, although if you have a high CEC substrate over it (like soil, clay, or organic potting mix) they will help grab onto the released nutrients and hold them for plant roots rather than letting everything immediately leach into the water column. I use these and have had great results. Overdoing these can lead to ammonia spikes, nutrient soup, and algae blooms, so use judiciously.

4. Root tabs fertilizer. Can be put under heavy root feeders, or used over the whole substrate on setup like osmocote.


And lots more I'm not remembering right now.

Probably the simplest is a layer of dirt covered with a layer of sand/gravel/safe-t-sorb. A lot of variables (substrate depth, level of fertilization, etc) depend on the kind of tank you want to set up, if you're doing a high-energy tank (med-high light, CO2) or a low-energy tank (low light, low to no added CO2), the kinds of plants you want to keep, the level of maintenance/trimming you'd prefer, the livestock you want to keep, deciding on whether you want a flat substrate or one with slopes, etc. Do lots of research. Dirt substrates can grow plants really well, but one con is that they are messy to change or remove (and messy when uprooting plants), so figure stuff out in advance so that you won't get three months in and realize you want to change your substrate around.

I like Dennis Wong's substrate overview HERE. My first planted tank waaaaaay back when used Jim Kelly's "Planted Aquarium Technology for the Very, Very Budget Minded" method (this is over 20 years old now!) and it worked great. I now run backyard dirt with a very small amount of compost mixed in, under a Turface cap (fired clay substrate like Fluorite), with Osmocote+ underneath and it's working great. Lots of methods can work great. Read about them all, decide what you want to try, and go for it.
 

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#1 Whatever soil you use, only use 1 inch of it. then cap with gravel or sand. miracle grow organic is a great starting point.
#2 Make sure you plan where your plants will be from the start. moving them gets very messy.
#3 Don't stock for several weeks or even months. Let the plants get grown in a bit before adding fish.

I've done a bunch of these: crypts, swords, and other heavy rooting plants love it.

enjoy!

Bump: #1 Whatever soil you use, only use 1 inch of it. then cap with gravel or sand. miracle grow organic is a great starting point.
#2 Make sure you plan where your plants will be from the start. moving them gets very messy.
#3 Don't stock for several weeks or even months. Let the plants get grown in a bit before adding fish.

I've done a bunch of these: crypts, swords, and other heavy rooting plants love it.

enjoy!
 

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I think the process is called deminerilizing soil...?

Better stuff than any typical top soil is the soil you find a couple feet down that's mostly clay fractions, silt and sand as it has little in the way of decomposing and composted dead stuff.

Still good to sift, soak and dry in the sun a few times.

Be careful about the Miracle Grow potting soil you buy, if it has composted chicken or other animal manures in it's list of ingredients, don't use it.
 

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Miracle Grow Organic Choice Potting Mix is what Walstad recommends in her book. I've used it with good success, but you can use something else that doesn't contain additives. MGOCPM actually contains chicken manure, which is fine to use. It'll leech ammonia for a little while, which is something to keep an eye on before adding livestock. In my experience, it's not an issue once the tank cycles properly.
 
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