How to Pick the Best Substrate for a Planted Aquarium

Welcome back to Part 3 of our Getting Started with Aquarium Plants series. In today’s article we will be discussing the topic of substrates for planted tanks. Substrate is the substrate, or the “soil,” at the bottom and which many plants use to grow roots and absorb nutrients. Some aquarium plants, such as rhizome, floating, and most stem, prefer to take nutrients from the water. Others, like vallisnerias, cryptocorynes and sword plants, prefer to feed their roots. The type of plants that you choose to keep will also affect the substrate selection.

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 contains many essential nutrients for plants, and the texture closely matches the lake bottoms or riverbanks where plants are found in the wild. But what do you get when you mix dirt with water? A big muddy mess. The majority of people solve this problem by sealing or capping the dirt. This prevents the dirt and water from clouding the water. This works well as long as the plants are not moved. 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 are made from nutrient-rich clay and topsoil to aid in the growth of plants that are heavy 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. These substrates become depleted of nutrients after one- to two years of regular use. They will then need to be remineralized just like Dirt Tanks. Nutrient-rich substrates are often the most expensive on the market. If you don’t have plants that primarily feed off their roots, there may be more affordable options.

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 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. Just regularly dose an all-in-one liquid fertilizer that contains most of the macronutrients and micronutrients your plants need. 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.

Rhizome, floating, and stem plants primarily absorb nutrients directly from the water column, so keep them well-fed with a comprehensive fertilizer like 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. Unlike regular aquarium gravel, these substrates are made of volcanic or clay-based gravel that usually have a higher cation exchange capacity (CEC). 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. Plus, as inert materials, they do not impact the pH, water hardness, or other water parameters in any significant amount.

Although almost any substrate material is suitable for growing aquarium plants, it is important to limit the size of the substrate. 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. You can also use large river stones for your ground cover. However, this leaves too much space between the pieces of the substrate, making it difficult for roots to grasp onto and establish themselves.

Regular gravel is compatible with Amazon swords, root-feeding plants, and other species as long you keep the substrate nourished with root tabs.

Which Substrate is Best?

There is no single right answer. It is impossible to simply look at an amazing aquascape and duplicate the substrate because every person’s water has its own unique characteristics. For example, in the world of gardening, serious hobbyists test their soil to find out what nutrients they have and which ones are missing. 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. Therefore, talk to other local planted tank enthusiasts who have similar water composition, and try different substrates and substrate mixes to find out what works best for you.

Very few plants in this stunning aquascape need substrate. So, a cheap and natural-looking sand was used as a cover for the tank’s bottom.

The key point is that you don’t have to spend a lot of money on expensive substrates in order to get amazing results. Be strategic about the plants that you will be using and the specific needs of each plant. If you are buying anubias but only one large root-feeding plant, mineralize the substrate around it to save money and then fill the rest of your tank with gravel. You don’t want to lower the pH or soften the water if you are making a tank for African cichlids.

Hopefully, this article has given you a good overview on planted tank substrates and which types are most suited for your particular needs.