Like the soil in a garden, the substrate of your aquarium will define how well your plants grow. While there are some plants that can grow in ordinary aquarium gravel, none will thrive. Typical aquarium gravel is inert and will not contribute to plant growth at all. Even plants that grow attached to driftwood like java fern or anubias benefit from the nutrients that planted substrates introduce to the aquarium. There are several options on the shelves to choose from.

Clay Gravel

Clay-based gravels are manufactured, as the name suggests, by adding nutrients to clay soil like late rite before firing it into hard, rock-like gravel. The exact nutrients included varies by brand, but they all have the same general benefits. Clay gravel is long-lasting and will not deplete or “run out” of nutrients within the lifetime of the tank. The pores in the clay will pull ions out of the water and make them available for plant roots to grab. And, clay gravels have an abundance of iron available for plant growth. The downside is that they cannot provide macro and micro nutrients to fuel fast growth and need to be supplemented if you want your plants to explode.

Aquarists will find clay gravel to be easy to use and easy to clean. In most respects, clay gravel is similar to ordinary aquarium gravel except for improving plant health. Clay gravels are somewhat limited in the nutrition they can provide for plants, so growth may be slower than with other options. Even if you are looking to get your plants growing quickly, clay gravel can be an excellent start, provided you are willing to add the necessary supplements.

Humate

The better option for faster growth is humate-based substrates. Humate fertilizers have long been used in agriculture and have recently made the jump to aquarium use. They are a mixture of volcanic soil,organic matter, and artificially added nutrients. Unlike clay gravels, humate gravels have many of the macro and micro nutrients needed by your plants readily available. Also, unlike clay gravels, they will deplete over time and need to be replaced periodically. They also tend to be messy as the humate pellet scrumble into loosely packed, nutrient rich mush, making it hard to vacuum your aquarium without also vacuuming up the soil.

Humate substrates will also need to be supplemented, but they tend to give much faster plant growth. They are a good choice for a densely-planted aquarium that won’t require much cleaning. They’re popular for tanks featuring neocaridina shrimp, too!

Soil

Some dedicated aquarists have even started using garden potting soil in their aquarium to really amp up their plant growth. Potting soil is very nutrient rich and with some care it will make your plants absolutely explode. The reason it hasn’t become mainstream is that it is incredibly messy and virtually impossible to clean. Potting soil is very light and loose so the slightest currents will send it swirling around in the water column. It’s absolutely possible to use potting soil, but not usually worth the effort to anyone but the most confident planted tank enthusiasts.

With the right substrate your aquatic plants will flourish, adding life and color to your aquarium. In the rest of this series of articles, we’ll cover other factors that contribute to healthy plant growth, including your lighting, choosing the right fish, and supplements to add necessary nutrients to the water. It may seem daunting, but with a little knowledge you’ll be more than capable of maintaining a beautiful planted aquarium.