How to Pick the Best Substrate for a Planted Aquarium

We are back with Part 3 of the 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. Therefore, the kind of plants you want to keep should affect your substrate choice.

Companies have spent a lot of time and research into developing plant-specific substrates to help plants grow well, but which kind is the 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 aquascaping and planted tanks became popular, people used soil to grow their 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. But what happens when you combine dirt with water? A big muddy mess. This can be fixed by covering the dirt with gravel or sand. It will prevent the dirt from clouding water. However, it is best to not move any plants. Also, soils eventually become depleted of nutrients (as it does with farming), which means the substrate must be reinvigorated somehow. 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 of nutrient-rich topsoil and clay to help grow plants that are heavy root feeders.

Due to the difficulty of maintaining dirty tanks, manufacturers developed specialized substrates for plants such as Aquavitro Aquasolum and ADA Aqua Soil. These compact, nutrient rich soil balls are sometimes called “active substrates”. Because they lower pH and soften the water hardness, many people use them in crystal shrimp tank and aquariums with large root-feeding plant populations. However, given that the substrates are primarily made of organic materials, they break down over time and become very muddy 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. Finally, nutrient-rich substrates are usually the most expensive option on the market, so if you are using plants that don’t primarily feed from their roots, there are more cost-effective alternatives.

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

Inert substrates are not as rich in nutrients as nutrient-rich substrates. This may seem bad, but it is important to keep reading. It is possible to set up a tank with rainbow gravel purchased at a pet store and then later add plants. This is because most plants rely on the water column for their nutrition. You can just regularly apply a liquid fertilizer that includes all the micronutrients and macronutrients 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.

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 of inert substrates for plants, including Seachem Flourite and CaribSea Eco-Complete. These substrates are similar to aquarium gravel but do not break down and can be easily replaced. 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. Inert materials don’t have an impact on the pH, water hardness, and other parameters of water in any significant way.

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. Coarse sand, however, creates small pockets between the particles and works much better as a planted 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 works well with Amazon swords or other root-feeding plants as long as the substrate is kept fertilized with root tabs.

Which Substrate is Best?

Unfortunately, there is not one right answer. You cannot just look at an awesome aquascape and copy the substrate it uses because everyone’s water is slightly different. For example, in the world of gardening, serious hobbyists test their soil to find out what nutrients they have and which ones are missing. The results may indicate that you need to amend your soil with peat, dolomite or another potting medium. 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. Aqua Soil mixed with Seachem Gray Coast is a good choice. It’s an aragonite substrate rich in these missing ingredients. Ask other local plant tank enthusiasts for advice and to help you choose the right substrate.

Very few plants in this beautiful aquascape require substrate, so a cheap, natural-looking sand was used to cover the tank 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. You should be careful about what plants you choose to use and what their needs are. If you buy a lot of anubias, but only one root-feeding or heavy plant in your corner, mineralize the substrate and then fill in the tank with a less expensive option such as 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.