Planting Your Aquarium: Soil or Potting Mix?

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Last Updated on 2023-08-30

When you want your fish tank to look its best, it’s important to use the best substrate. Not only that, but it is also important for the health of your fish and other aquatic pets, as well as the plants in the aquarium. But when it comes to plants, nothing works as well as good old soil, and yes, it works in aquariums too. But before you start shoveling, there are a lot of things that need to be taken off before you can use soil. This article will tell you what you need to know about using potting mix or soil in your planted aquarium.

Table of Contents

Is Potting Soil Safe For Aquariums?

You might be surprised to find that some aquarists use soil as the bottom of their tanks. You might also wonder if it’s safe or if it will hurt your aquarium plants or fish. However, using soil in an aquarium is actually safe, and it even has a lot of uses and is great for your plants as well.

In your aquarium, you should only use potting soil or a mix that’s organic. This is because they won’t have any pesticides, fertilizers, or other chemicals that could be bad for your fish. Make sure not to use too much, and cap the top off with something inert, like sand or gravel, to keep the nutrients from getting into the water and making it look muddy.

You can find a wide variety of commercial potting soils at any major garden store. To avoid harming your plants, make sure the potting soil or mix you use is organic and contains no synthetic fertilizers. If you can’t tell if a product contains organic ingredients, keep looking until you do.

What Potting Soil Can I Use In My Aquarium?

There are a lot of good reasons to use potting soil in your aquarium, so maybe you’re ready to give it a try. But there are a lot of different kinds of potting soil, and not all of them can be used in an aquarium. Here are some types of potting soil you can use in your aquarium.

1. Indoor Potting Soil

Indoor potting soil is made for houseplants like peace lilies, philodendrons, and snake plants, but you can still use it for plants in your aquarium. It has things like biochar and sandy soil that help with drainage and keeping nutrients in the soil. Most indoor potting soils don’t have peat and don’t have any artificial fertilizers.

2. Garden Potting Soil

Most of the time, garden potting soil is used to improve the soil. You can add it to your garden, use it to fill in your lawn, or put it in aquariums as a base. It usually has native soil, sand, perlite, as well as clay in it. These things improve the soil’s structure and level of organic matter, but make sure to sterilize it before you use it.

3. Seed Starting Potting Soil

Most seed-starting potting soil is a low-nutrient mix that has little to no soil. But this potting soil will have things like perlite or coco coir to help the roots of your aquarium plant roots drain and breathe. This helps the roots of plants branch out in search of nutrients, which can help your aquarium plants grow quickly.

4. Moisture Holding Potting Soil

Moisture-holding potting soil is made with things like peat moss, yucca extract, and biochar, which helps the soil hold on to water. These things keep the potting soil from dehydrating and retain water in it so that your aquarium plants can use it. It also keeps the soil moist without letting too much water in or suffocating the roots.

5. Orchid Potting Soil

Orchid potting soil is great for aquarium plants that need a lot of air and water to drain away. Soil amendments like coconut coir, fir bark, and charcoal are added to orchid potting soils to help with this. These ingredients make it easier for plants to get enough water without letting the roots stay wet.

6. African Violet Potting Soil

This potting soil is a little bit acidic, but it holds water well, has great aeration, and lets water drain well. This potting soil is made of peat moss, limestone, and some perlite. When used in aquariums, it may lower the pH level of the water.

Aquarium Tank, Aquatic Plant Layout with White Cloud Minnows and Cherry Shrimps

What Is The Difference Between Potting Soil And Potting Mix?

You might get confused about potting soil and potting mix because they sound the same and may be the same thing. But they’re not the same and can’t be used in the same ways. In this list, we’ll tell you how potting soil and potting mix differ.

1. Content

Potting soil is different from a potting mix because it has garden soil in it. Potting soil also has minerals and organic material in it, which means it could have weed seeds, compost, as well as fungi or other diseases that can make plants sick. 

2. Usage

Even though the word “potting” is in the name, potting soil is not used in pots. Instead, it is used for gardening and landscaping that doesn’t involve pots. Potting mix, on the other hand, is a much better way to grow plants in pots than potting soil because it is easier to control. 

3. Density

Because of what’s in it, the potting mix is light and fluffy. On the other hand, potting soil is made up of soil and organic material. However,  this can be a problem if the potting mix is put in an aquarium because the materials will likely float to the top.

4. Affordability

When compared to those other gardening mediums, potting soil is typically quite cheap. Which is one of its many advantages. Plus, you can easily access potting soil from your own backyard. 

5. Aeration and Drainage

When compared to potting soil, potting mixes allow for greater air circulation and water drainage. This is because of peat moss, vermiculite, and other things that are added to the potting mix making it light and fluffy. Potting soil, on the other hand, is easy to get compacted in a container, resulting in less aeration.

6. Durability

Because it is mainly composed of dirt, potting soil will exceptionally last longer. On the other hand, the organic components of potting mixes will break down over time. When this happens, the potting mix will be useless.

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How Do You Use Potting Soil or Mix In An Aquarium?

Using potting soil or mix in an aquarium has many benefits, so you might want to use it. But it’s not as easy as you might think, and you might need to take a few extra steps to set it up right. Don’t worry because here is a step-by-step guide to using potting soil or mix in your aquarium.

1. Sterilize the Soil

To sterilize the soil, just sprinkle Hydrogen Peroxide on your potting soil or mix and make sure to clean it well. You can also bake the soil at 180 to 200 degrees Fahrenheit for 30 minutes or heat it in a microwave for 30 minutes. After sterilizing it, let it cool down before using.

2. Soak the Soil

Let the soil soak in dechlorinated water for a couple of hours before placing it in the aquarium. This will make the extra debris float to the top, where it can be easily removed. This will also let extra gas bubbles out from the soil, which is better for the plants in your aquarium.

2. Place the Soil In Aquarium

Many aquarists say that you only need to add an inch of potting soil or mix to the bottom of your tank if you want to use it as a substrate in a planted aquarium. If you don’t put too much soil in your aquarium, it won’t leak too much ammonia and nitrates into the water. This will also keep your aquarium from getting a bloom of algae.

3. Put the Plants In The Aquarium

Once the soil is in place, you can put the plants on the substrate. This makes it easy for you to get to the soil and put the plants where you want them. But make sure it’s where you want the plants to go because once the water is in the aquarium, it is not advisable to remove them.

4. Cap The Soil With Inert Material

After you put down the soil, cover it with a 2-inch layer of something that won’t move, like sand or gravel. This extra layer will keep the soil or mix from washing away into the water column. When potting soil or mix is added to a new tank, it will make some bubbles and move the capping substrate a little bit, but it will settle down after a few weeks.

5. Slowly Pour Water

Make sure to put something on top of the inert material, like a plate or a slightly inflated plastic bag, before you pour the water into the aquarium. This is so that you can pour water over it instead of letting it hit the sand and soil directly. This keeps the water from stirring up the soil too much.

6. Wait For The Dirt To Settle Down

No matter how carefully you fill it, the very first time you use soil, the water will probably be cloudy to some extent. This is normal, and things should get back to normal in the first two weeks. If your sand is dusty, power filters will help your water clear up a lot.

What are the Benefits Of Using Potting Soil or Mix in a Planted Tank?

Many aquarists might wonder if it’s safe to use organic potting soil in an aquarium. It might be surprising to know that, yes, it is and one of the best ways to ensure your fish and plants are healthy is to use organic potting soil. In this list, we’ll talk about the benefits you’ll get for using potting soil or mix in your planted aquarium.

1. Beneficial Bacteria

There are a lot of good micronutrients and macronutrients that plants can use in both potting mix and soil. Because of this, it is possible to have a beautiful aquarium with plants that thrive without adding more CO2.

2. Full of Nutrients

Soil is most likely the best substrate for any aquatic plants, and a high-tech planted tank can’t be made without it. When planted in aquarium soil, plants that get most of their food from their roots will do well.

3. Natural and Healthy Environment

Both plants and fish love nothing more than a natural environment, and silt and natural soil are the most natural things you can find. By using organic potting mix or soil as the substrate of your aquarium, you give your plants the best chance to grow healthy, which also makes the fish happier.

4. Soil Improves Water Quality

Organic potting soil can help you grow big, healthy plants, and it can also help you keep your fish in a more natural environment. The organic material in the soil can filter out and break down toxins and other pollutants in aquarium water, which helps keep your aquarium in great shape. If you let plants grow more, they will make more roots which can then be used to soak up any extra nitrates in the water, making your aquarium better overall.

5. It Anchors Plants In Substrate

All of these extra roots not only look great and help improve the quality of the water, but they also help hold plants in place. When using potting soil or mix as the bottom substrate of your aquarium, your aquatic plants will be able to develop deep roots, which will help protect them from strong currents or any fish that loves to dig. 

6. Cheaper Substrate Option

Potting soil is a lot cheaper than gravel or rocks as an aquarium substrate, and you can find it at most garden stores. This means that using potting soil or mix as your substrate in your aquarium will save you a lot of money over time. It’s also very simple to make at home.

7. Sustainability

You won’t even have to think about replacing the soil’s nutrients for years. Unlike with some other substrates, you don’t have to fret about adding new soil to your tank often. Once it’s set up, you’re good to go, making it a great way to grow plants that are beneficial for both the environment and your pocket.

When Should You Use a Potting Mix or Soil In An Aquarium?

You may have heard or seen that potting mix or soil is good for your aquarium. But it can be used for many things, and it’s not always the best substrate. Here are some reasons why you might want to use potting soil or mix in your aquarium.

1. Setting Up Planted Aquariums

The soil substrates will give plants the nutrients they need to grow better and give them something stable to hold on to. But setting it up is hard, and if it’s your first time, you might make the water cloudy or cause a bloom of algae. If you don’t want to put live plants in your aquarium, there is no reason to use potting mix or soil.

2. If You Have a Big Aquarium

Any size aquarium is suitable for holding potting soil or mix. However, fish could not have as much space as you’d like in aquariums that are 12 inches or less in height. This is due to the fact that 9 inches is all that’s left over after covering an inch of potting soil or mixing the base layer, then covering it with 2 inches of gravel or sand.

3. Cheap and Accessible Substrate For Plants

If you want to have plants in your aquarium, you might need to get a substrate. But substrates that you can buy at local pet stores are often expensive and sometimes not even available. Soil is also easy to use because you can use the soil in your garden as long as it is clean and free of pesticides.

4. When In Need Of Sustainable Substrate

Like any other part of an aquarium, aquarium substrates will need to be replaced every so often. The good thing about using potting mix or soil, though, is that it doesn’t need to be replaced as often. The soil can hold nutrients and good bacteria that would last for many years.

5. Aquascaping

When aquascaping, it’s important that the aquarium’s substrate is stable and doesn’t move around. It’s also easy to put driftwood and other aquarium decorations in it because it doesn’t get powdery and make your aquarium look muddy, especially when it’s compacted. It’s also great for giving your aquarium a natural and dramatic look.

How Much Potting Soil Should You Use in an Aquarium?

Using potting soil or mix as a substrate can help your aquarium in many ways. The soil has a lot of nutrients that are good for plants and some types of fish. But you can’t just put in any soil you find because setting up an aquarium with soil substrate takes a little more work and planning than the usual way.

It’s important not to put too much potting soil inside an aquarium because the soil has a large amount of nutrients that can cause an algal bloom or an ammonia spike if it’s not set up right. Expert aquarists say that an aquarium should have an inch of potting soil or mix. But if you have more than 40 gallons, you might want to make the soil layer 1.5 inches thick.

Generally speaking, potting soil already has a lot of nutrients in it, so you don’t have to add very much. That’s why it’s important to put 2 inches of sand or gravel on top of the soil. The inert material will keep the soil in place and stop the nutrients from getting into the water.

How Long Does Potting Soil Last in Planted Tanks?

There are many good reasons to use potting soil or potting mix as the bottom of your aquarium. The soil gives your plants a stable place to grow, and because it is full of nutrients, your aquarium plants will always get the food they need. Also, a soil aquarium substrate will last longer than other types of substrate.

A good quality potting mix will last for at least about a year before it begins to show indications of nutrient deficiency. Some potting soils include a trace amount of organic soil, which can extend the life of your plants because of the bacterial activity and broken-down organic matter. By adding soil additives, however, you can make your potting mix or soil last for years.

Like any other substrate, it will last longer if you clean and take care of it regularly. The best thing about using soil as a substrate is that it can last for a very long time before it needs to be replaced. When aquarium fertilizers or root tabs are used regularly to improve the soil, they can last up to 5 to 10 years.

Can You Use Miracle Grow Potting Soil In An Aquarium?

If you want to set up a newly planted aquarium, you can, in fact, use potting soil as the bottom layer. There are many different kinds of potting soil that you can buy at the nearest gardening store. But you can’t use all kinds of potting soil as the bottom of your aquarium.

When choosing potting soil or potting mix as an aquarium substrate, it’s important to choose one that is organic and doesn’t contain chemicals and fertilizers. A lot of common soils, like Miracle Grow, are made to help plants grow by adding chemicals and fertilizers. Since it is designed only for plants, Miracle Grow poses a health concern for fish when used in an aquarium.

Also, the chemicals in these soils will also be bad for the water in the aquarium and may drastically change the pH levels of the water. This will make it hard for most fish to live in your aquarium. Before you use potting soil or mixes, make sure they are made of only organic materials.

How To Make Your Own Aquarium Soil

One of the best things about using soil as a substrate is that it can be found almost anywhere. Even the ones in your own backyard. But before you start putting it in your aquarium, you should do these things to make sure it is safe for the fish and other animals in your aquarium.

1. Collect Soil

You can use a trowel and a bucket to collect garden soil and make sure to get soil from places that haven’t had chemicals or fertilizers for a long time. You can also purchase potting soil at any garden store, but only if it says “organic” or “chemical-free” on the bag. Be careful with bags that have peat moss in them because peat moss can lower the pH level of your aquarium.

2. Filter The Soil

After you collect soil, you should sift it to get rid of rocks, sticks, bugs, and other things. This is so that things that don’t belong in your aquarium can’t get in and hurt your fish or make the water unstable. Sift enough to make a layer in your aquarium that is an inch or two deep.

3. Sterilize

Put the sifted soil on a baking sheet and bake it for 30 minutes at 200 degrees Fahrenheit. This kills all the microorganisms, seeds, and other things that don’t belong in the soil. After that, let it cool down for another 30 minutes.

4. Place The Soil Into The Aquarium

Spread the soil out on the bottom of the aquarium. You will only need a very thin layer of about an inch, and your aquarium plants will do just fine. For a 40-gallon aquarium, you can use 1 and a half inches.

5. Cap with Inert Material

Cover the surface with a 2-inch layer of an inert material like gravel or sand. This will keep the soil from being stirred up and make your aquarium a muddy mess while letting the roots reach the nutrients below. By capping it, nutrients that could cause spikes in ammonia or algae blooms won’t get into the water.

6. Slowly Add Water

After doing everything above, you can slowly pour water into the tank. If you don’t want to stir up the substrate, it might help to pour it onto the sides. Now that it is full of water, you can start cycling your aquarium.


Can You Use Normal Soil in An Aquarium

You can use regular soil, as long as you know it hasn’t been treated with chemicals like pesticides and fertilizers. It’s important that everything stays natural.

Can Potting Soil Be Used for Aquarium Plants

Potting soil can be used safely in freshwater aquariums with plants. As long as they are organic and don’t have any harmful fertilizers or pesticides.


As long as it is organic, potting soil or mix can be used in aquariums. There are many types of potting soil or mix that can be good for aquariums. It also costs a lot less than other aquarium substrates and has many of the same benefits. When setting up a soil substrate in an aquarium tank, make sure to cover the dirt with a layer of gravel or sand that is 2 inches thick so that dirt doesn’t get into the water or ammonia doesn’t leak out. Overall, potting soil can be a good choice for aquariums if you get it from the right place.

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