Dirted tanks Best Methods For Preparing Organic Soil For An Aquarium

Best Methods For Preparing Organic Soil For An Aquarium

A great way to prepare organic soil for an aquarium is by adding peat moss, manure, iron oxide, bonemeal, bloodmeal and Osmocote. These additives provide aubstantial nutrition for healthy pllant growth in a dirted aquarium.

The purpose of preparing your soil and using additives

The purpose of using additives in your organic soil is to prolong its life. Here’s why:

One of the benefits of a dirted tank is that they can last for many years while still providing nutrition to plants. This is something that commercial aquarium substrates can not accomplish without regularly supplementing fertilizers, such as root tabs.

But in order for a dirted tank to last for so long, it needs anaerobic bacteria and other forms of microscopic life that will convert waste into macro and micronutrients that the plants can consume.

The processes that allow this microscopic life to occur may take a year or more to occur.

This means the organic soil we start our tank with must be able to provide our plants with nutrition for a year or more until these micro-organisms can start producing plant nutrition of their own.

How do micro-organisms create plant nutrition?

Bacteria eat protozoan waste, protozoan eat fish waste. Anerobic bacteria break down waste into elements that plants can take up into their roots. They also produce nitrogen gas, which is released into the air.

Additives that will prolong the life of your aquarium’s organic soil

Here is our recommended list of additives to consider when setting up a new dirted tank. We have provided an estimate of how much you should add based on a 20-gallon tank.

Our newly setup dirted tank

Your dirt layer should be about 1-inch deep, with a 2-inch cap. If you end up with less than 1-inches for your dirt layer then simply mix in more of your organic soil.

Our dirted tank after 1 month

The following ingredients and additives can be bought from a local nursery or home and garden store.

Organic peat moss (4 cups)

Peat moss has several useful properties. Most notably, it has a high cation exchage capacity (CEC). This means it is capable of absorbing and storing a substantial amount of fertilizers from the water around it, which then get use by plant roots.

It will also soften an aquarium’s water slightly. Most aquatic plants tend to grow better in neutral or slightly acidic water.

Peat moss also contains tannic acid, which is proven to improve fish immunity and contain antibacterial properties.

Organic potting soil, organic top soil or organic garden soil (4 cups)

Organic soils contain microorganisms, decaying plant material and other organic matter that provide nutrition to plants and will help establish a sustainable nitrogen cycle.

In our experience, cycling a dirted tank was quite easy for this reason.

The organic soil we used for our 20-gallon tank

It’s important to buy organic soil to ensure you’re not adding harmful fertilizers or chemicals to yoru aquarium.

Manure (2 cups)

Manure is an excellent natural fertilizer that has big benefits for aquatic plant growth. It contains nitrogen, phorphorus and potassium (known as NPK), plus other nutrients.

These are key macronutrients that are required in large amounts in order for plants to grow successfully.

Iron oxide (2 heaping handfuls)

Iron is considered a micronutrient because plants require only a small amount of it. However, it plays a crucial role in healthy plant development.

Iron helps plants produce chlorophyll, a pigment inside of their chloroplast organelles that allow the plant to absorbs energy from light. This is a fundamental requirement for photosynthesis to occur.

Bonemeal (handful)

Bonemeal is added mainly to provide a source of phosphorus, which is a plant macronutrient.


Bloodmeal (handful)

Bloodmeal is a source of nitrogen that will be consumed rapidly by pretty much all aquatic plants.

Osmocote (small handful)

Osmocote is a concentrated fertlizer that tcontains NPK, but also acts as a source of ammonia. Normally, aquuarists view ammonia as something to get rid of because it’s harmful to fish. This is true.


However, ammonia is taken up readily by aquatic plants. In fact, when given the choice between ammonia and nitrogen, plants will utilize the ammonia first.

When added to a dirted tank, where it will will have a substrate cap, Osmocote will not leech into the water column and harm fish. Also, ammonia binds to organic material such as soil.

This is a great additive for heavily plantted tanks. Especially if you’re adding heavy root-feeding plants such as Amazon swords or crypts.

How to prepare these soil additives together

Add the dry ingredients and mix together

Begin by mixing all of the dry ingredients together. You can do this in your tank or in a separate 5-gallon pail. We prefer the pail method because it’s less likely to mke a mess in your aquarium.

Add water to create a mud

Next, start adding a littlle bit of water until your mixture gets to a muddy consistency. You don’t want it to be soupy or water. You want it to be firm enough that the cap sits on top and does not mix in with it.

If you added too much water you can take a fish net and scoop out some of the mixture and then squeeze it in the net over a bucket. This will get rid of some moisture.

Add a border of substrate cap along the perimeter of your tank (optional)

We like to build up a border of sand around the perimeter of the tank’s bottom to contain the soil from the edges. Also, because we prefer the look of a solid substrate along the outside of the tank versus a layered strata.

The purpose of the substrate cap is to prevent the soil from leeching into the water column above. One possible vulnerability is around the edges of your tank where a disturbance may causue the soil to leech upwards.

This is another reason we like to create these borders and keep the soil away from the exact edge of the aquarium walls.

Add a 1-inch layer to the bottom of your tank

Next, we will add the muddy mixture to the bottom of our tank, creating a 1-inch layer. We simply use a scoop or our hands so we can mroe carefully place the soil.

Add a 2-inch substrate cap

Finish it off witha 2-inch layer of your substrate cap. We recommend snad because it it the most secure and compact cap. This will ensure nothing leeches into your water column. We’ve never had any problems with leeching or cloudy water this way.

Super Naturals aquarium sand that we used

You may hear some people advise against using sand for a couple reasons.

First of all, they believe that sand is too compact to allow plant roots to grow. That’s simply not true. We have a thick 2-inch cap of sand with plants that are growing like mad.

Another reason is because they believe a dense sand cap will prevent oxygen from reaching the bottom of the tank. This is absolutely and actually one of the things we want to happen.

Below about 2-inches of sand, there will be little to no oxygen available. This creates an environment for anaerobic bacteria to grow. This bacteria is what will eventually convert waste in our aquarium into nutrients for our plants to grow, creating a sustainable aquarium ecosystem.

Ryan Ferguson

Founder, Rooted Tank

Ryan Ferguson, the founder of Rooted Tank, started fishkeeping in 2019. He has continued to level-up his planted aquarium skills and wanted to share his journey and knowledge with other aquarists.



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