Substrate for a Planted Aquarium – Everything You Need to Know

As a young fishkeeper, I spent money and time on plants like Amazon swords, Vallisneria, or Cabomba that invariably died when I planted them in gravel without added nutrients. There’s no need for you to suffer as I did.

Next to appropriate lighting, choosing the right substrate for your planted aquarium is the most critical element to consider. Let’s take a closer look, and help you build the planted tank of your dreams.

Do Aquarium Plants Need a Substrate?

A lot of aquarium plants don’t technically require a substrate. Most plants can feed through their leaves (foliar feeding) or aerial roots. 

Many of the plants we keep aren’t true aquatic plants. A reasonable percentage of them originate in places like the Amazon Rainforest.

During the flooding season, these plants find themselves submerged for up to six months, and have adapted accordingly. Though they can survive in water permanently, they’re used to growing in soil and taking in nutrients through their roots. 

Humans can survive on liquids. But will that lead to the biggest, strongest, most well-adapted people? Probably not. In the same way, if you want your beloved plants to thrive, they need an excellent aquarium substrate.

Substrate Helps Plants to:

  • Take in additional resources and nutrients through their roots
  • Remain anchored against currents, and remain stable when bumped by fish
  • Have exposure to abundant nutrients, as well as optimal pH and water hardness levels
  • Cultivate beneficial bacteria that protect them against disease and help them use available nutrients

What’s the Right Substrate For My Plant?

Different types of plants do well with various substrates. Below, we’ve divided the plants into different categories. We’ll mention a few plants of each type, and describe the substrate they prefer.

Free-Floating Plants

These plants typically grow without any attachment to the substrate. 

Water lettuce

Examples include:

  • Carolina fairy moss
  • Water lettuce
  • Butterfly ferns
  • Duckweed
  • Indian fern

As you may imagine, most free-floating plants don’t need a substrate since they’re not attached anywhere. They have a network of fine roots that remove nutrients from the water. In some cases, like butterfly ferns, they also take in nutrients through small hairs on their leaves. 

Indian ferns (or water sprites) are an exception and may grow as either a floating plant or a substrate plant. When planted they prefer a dense layer of gravel or sand. 

Submergent Plants

Most of the aquatic plants we grow are submergent, remaining below the water’s surface, with roots in the substrate.

To make substrate selection easier, it’s best to consider them in terms of their root structure. They may be:

  • Root feeders that draw their nutrients from the substrate
  • Rooted plants that feed mainly through aerial roots, but take some nutrients from the substrate
  • Plants that feed solely through aerial roots and leaves

Ground Root Feeders

These plants absolutely need substrate and draw all their nutrients from it. They may be divided into two categories:

  • Plants with thin, hair-like roots
  • Plants with tap roots or multiple sturdy roots

Plants with Thin, Hair-Like Roots

These plants need a substrate with fine particles to allow their thin roots to spread. They prefer sand, peat, or soil mixes. Peat is best for plants that like acidity, while sand is the most stable option for the rest.

Echinodorus Isthmicus by Kurt Stüber CC BY-SA 3.0.

Examples include:

  • Amazon sword plants (Echinodorus sp.)
  • Sagittaria
  • Vallisneria
  • False Tenellus

Plants with Sturdy Roots

These plants may also create substantial root networks, but their roots are much thicker. They do well in gravel and clay pellets as long as you feed them regularly, or layer in some kind of nutrient-rich substrate as well.

Examples include:

  • Cryptocornes
  • Red tiger lotus
  • Banana plant
  • Onion plant
  • Madagascan Lace Plant
Madagascar Lace plant

Anchored Aerial Root Feeders

Some plants also use nutrients from the water, though they’re anchored in the substrate. They’ll do well in a layered substrate containing both coarser and finer materials.

 Examples include:

  • Some species of Vallisneria
  • Certain Cryptocornes
  • Some Anubias
Anubias by Ji-Elle CC BY-SA 4.0.

The best thing for these plants is a mix of clay pellets or gravel with some sand, peat, or soil blend. Remember to add liquid fertilizer to the water regularly, as they feed mainly from the water column.

Unanchored Aerial Root Feeders

These types of plants generally have sturdy aerial roots, with a network of finer roots growing out of them. They take most, if not all, of their feeding from the water column.

Examples of these plants include:

Java Fern by ictheostega CC BY 2.0.

You can attach these plants to the substrate, but you can also attach them to any ornament in the tank. They have no substrate requirements but do need water with sufficient nutrients.

Emergent Plants

Emergent plants are a somewhat unusual group of plants. They naturally grow on the substrate at the bottom of bodies of water. However, they usually extend to grow (at least partially) above the water’s surface. 

Examples include:

  • Water lilies
  • Water celery
  • White top star rush 

Some people consider water lilies a floating plant (because their leaves float on the surface). Since they’re attached to the substrate, they’re truly emergent. 

As with most emergent plants, water lilies require a rich substrate. 

They have a long tap root, and plenty of finer roots, and will take readily to sand, soil mixes, or even peat. The main concern is that they need plenty of nutrients.

FAQ

What is the Cheapest DIY Option?

Organic potting soil or compost combined with sand or gravel is probably one of the cheapest soil mixes for planted aquariums. However, it may affect water acidity and hardness. Place some of the soil mix in water and test these parameters to see how it affects them before using the mix.

Can I Use Normal Garden Soil In My Tank?

If you have a garden that you know doesn’t get exposed to herbicides, insecticides, or other pesticides, you can try using garden soil in your tank. As mentioned above, test how it affects water acidity and hardness before using it. 

You may also want to give it a few days to soak, so you can remove any floating particles. Finally, I’d recommend testing it out on a small amount of fish, rather than the main aquarium.

How Deep Should A Planted Aquarium’s Sand Be?

Typically, you want a substrate between one and two inches deep in your planted tank.

What Is Layering And How Why Is It Used In Planted Tanks?

Layering is when you place different substrates in layers in your aquarium. It’s often used in planted aquariums because it allows you to meet the need of all the different plants. 

I.E. You can have gravel layered at the surface for a plant with coarse roots, while another area has a sand layer at the surface to make room for Amazon sword plants.

Can I Root Plants in Sand?

Yes, but it will be more difficult than some other substrates because it doesn’t allow easy water flow and can be dense. When using sand, it’s best to layer with gravel, pebbles, or clay pellets so that the substrate gets some water flow.

What Are Root Tabs, And How To Use Them

Root tabs are special capsules containing fertilizer that help give your aquarium plants and substrate the appropriate amount of nutrients. 

Using them is simple, just bury them (in rows) in the substrate every five to six inches. You should place the rows around five to six inches apart so that all the substrate has adequate nutrients.

How Do I Make My Own Root Tabs?

There are a couple of ways to make your own root tabs, but here are my two favorite ideas:

  1. Sun-dry some rabbit droppings – Rabbits have some of the most nutritionally-balanced manure. They also decompose slowly, so they’re perfect as plant feed. If you have rabbits or know someone who does, you can easily dry their droppings in the sun, and bury them the same way you would root tabs.
  2. Make a mix of organic, non-toxic fertilizer, and freeze it in an ice cube tray. Then, take the individual ice cubes and bury them as you would root tabs. Unlike rabbit poop, this is a quick-release approach. 

Final Thoughts

Depending on the species in your planted aquarium, the substrate can make a huge difference. Some plants require a wealth of substrate, while others barely need any.

We hope that this guide has helped you come to terms with the different types of plants and what substrate is best for them. If you still have questions, please feel free to contact us. We’d love to help you find the ideal mix for your plants and make your planted aquarium look great.

About the author

AboutHi, I’m Johanan! I love animals of all shapes and sizes, but especially fish. I’ve gone from working at a pet store as a teenager to keeping and breeding Bettas and other fish at home. My passion for fish is endless! the author

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