How to Pick the Best Substrate for a Planted Aquarium

We are back with Part 3 of the Getting Started with Aquarium Plants series. Today’s article will explore the topic of tank substrates. Substrat is the “soil” or ground at the bottom of an aquarium. It is what many living plants require to grow roots and absorb nutrients. Interestingly, some aquarium plants (e.g., rhizome plants, floating plants, and most stem plants) prefer to absorb nutrients directly from the water, whereas others (e.g., sword plants, vallisneria, cryptocorynes, and certain carpeting plants) mostly feed from their roots. Your choice of substrate should be based on the type of plants you wish to keep.

Research and companies have spent much time developing substrates for plants that are plant-specific. But what kind of substrate is best? This article will give you a basic overview of the different types of substrates, so that it is possible to customize them to your specific needs. Let’s begin by focusing on the two main types: nutrient rich and inert substrates.

Nutrient-Rich Substrates

Before the popularity of aquascaping and planting tanks, people relied on soil to grow plants. Organic soil has many of the essential nutrients plants need and is similar to the riverbanks and lake bottoms that plants find in nature. What happens when you mix dirt and water? A big muddy mess. Most people fix this by capping or sealing the dirt under a layer of gravel or sand to prevent the dirt from clouding the water, which works okay as long as you never move any of the plants. It is possible for soils to become depleted of nutrients over time, just as farming does. This means that the substrate must be renewed. You can either pull out the plants and let the “land” lay fallow while the fish waste reintroduces nutrients or you can remineralize the soil with root tabs and other fertilizers, but both methods tend to cause very murky water that is difficult to clear up.

Easy Root Tabs contain nutrient rich topsoil, clay, and other ingredients to support the growth of heavy root feeders.

Because of the difficulties that come with maintaining dirted tanks, manufacturers created specialized plant substrates such as ADA Aqua Soil and Aquavitro Aquasolum. These compact, nutrient-rich balls of soil are also known as “active substrates” because they tend to lower pH and soften water hardness, so many people use them in crystal shrimp tanks and aquariums with heavy root-feeding plants. The substrates are made primarily of organic materials so they can break down and become muddy just like regular dirt. After one to two years of usage, these substrates also become exhausted of nutrients and will need to be remineralized like dirted tanks. Final note: Nutrient-rich substrats are typically the most costly on the market. This is because plants that do not rely on their roots for food will have to pay more.

Crystal shrimp tanks with large root feeders and planted aquariums that have a lot of fish are able to use nutrient-rich substates. However, they need to be replenished with new nutrients regularly and can break down over time.

Substrates that are inert

Unlike nutrient-rich substrates, inert substrates come with very few nutrients, which may sound bad at first but keep reading. If you buy rainbow gravel at the pet shop and later decide to add plants, it should work fine for most stem, floating, or rhizome plants. They primarily feed from the water column. Regularly apply an all-in-1 liquid fertilizer, which contains the majority of the micronutrients as well as macronutrients that your plants require. To convert an inert substrate to a nutrient rich substrate, insert root tabs if you are adding a heavy root feeder such as an Amazon sword.

The primary way that stem, floating and rhizome plants absorb nutrients is through the water column. Keep them well-fed using Easy Green.

There are many brands available for planted tanks such as Seachem Flourite or CaribSea Eco-Complete. Like aquarium gravel, they do not tend to break down over time and therefore do not need to be replaced over time. This substrate is made of volcanic and clay-based gravels that have a higher cation Exchange Capacity (CEC) than regular aquarium gravel. This simply means the materials are better at holding onto nutrients (such as from fish waste or fertilizers) so that plants can easily use them for greater growth. Inert materials don’t have an impact on the pH, water hardness, and other parameters of water in any significant way.

You can grow aquarium plants with almost any type of substrate material. However, you should avoid extremes in terms of substrate size. Fine sand can be hard for plants as the small particles tend to compact and make it difficult to spread roots through. However, coarse sand creates smaller pockets between the particles, and is better for use as a tank substrate. If you use large river rocks as your ground covering, it will leave too much space between each piece of substrate. This makes it difficult for rooted plants and makes it more difficult to grab onto the surface.

Regular gravel works well even with Amazon swords and other root-feeding plants, as long as you keep the substrate fertilized with root tabs.

Which Substrate is Best?

Unfortunately, there is no one right answer. You cannot just look at an awesome aquascape and copy the substrate it uses because everyone’s water is slightly different. In the world of gardening, hobbyists can test their soil to determine what nutrients are present and which ones they lack. Based on the results, you may need to amend your soil by adding dolomite, peat, or other potting media. If you live in a region that has soft water, then you may need to add ADA Aqua Soil, which further softens the water. This could cause your plants to be deficient in key nutrients like calcium, magnesium, or manganese. In order to compensate, your optimal substrate choice may actually be a mixture of Aqua Soil and Seachem Gray Coast, an aragonite-based substrate high in those missing ingredients. Talk to other enthusiasts with similar water conditions and test different substrates to discover what works best.

Very few plants require substrate in this beautiful aquascape, so a low-cost, natural-looking sand used to cover the tank base.

The key point is that you don’t have to spend a lot of money on expensive substrates in order to get amazing results. You should be careful about what plants you choose to use and what their needs are. If you’re buying mostly anubias and only have one heavy root-feeding plant in the corner, save your money by mineralizing the substrate right around it and then fill in the rest of the tank with a cheaper option like gravel. When you make a plant tank for African Cichlids, you don’t want the water to be lower pH or softened.

This article should have given you an overview of the different types of substrates for planted tanks and which ones are best suited to your specific needs.