Planted Aquarium Substrate: Soil, Gravel, and Sand

Are you considering starting a new aquarium and wondering which substrate would be the best choice for your setup? Or perhaps you're contemplating whether you even need substrate at all? Each aquarium has its own unique style and layout, serving either functional or aesthetic purposes.

In this article, we will explore the advantages and disadvantages of bare-bottom tanks versus tanks with substrate. Additionally, we will delve into the pros and cons of the three main types of substrates commonly used in the freshwater aquarium hobby: gravel, sand, and soil.

Bare-bottom vs. Substrate

A bare-bottom aquarium refers to an aquarium setup without any substrate. One of the key advantages of such setups is their ease of cleaning. Maintenance can be as simple as performing regular water changes.

Without substrate, fish waste and uneaten food have nowhere to accumulate, allowing the water flow to easily push debris into the filter. In cases of low water flow, any detritus that settles on the tank bottom is clearly visible and can be easily removed using a siphon.

Bare-bottom tanks are particularly well-suited for breeding and quarantine purposes. The cleanliness of the water plays a vital role in maintaining the health of the fish, making bare-bottom tanks a popular choice among breeders.

While bare-bottom aquariums are practical and easy to maintain, they may not be visually appealing compared to aquariums with substrate. The reflective nature of the bottom panel can create an unattractive mirror effect that detracts from the overall aesthetics.

By adding substrate to the aquarium, you can achieve a more natural and visually pleasing look. Substrates also provide a habitat for beneficial bacteria to colonize, which is essential for the nitrogen cycle. These bacteria play a crucial role in converting toxic ammonia into less harmful nitrates. Without substrate, the available surface area for these microorganisms to thrive is significantly reduced.

In addition, certain fish species and tankmates benefit from the presence of substrate. Bottom-dwelling species like Corydoras and loaches feel more secure and enjoy interacting with soft substrates. Moreover, specific types of soil can create an ideal environment for shrimp by lowering the water's pH.

• Disclosure: Using an aquarium soil substrate is essential for creating a thriving and visually stunning planted tank. Artificially dyed gravel or sand lack the necessary nutrients that plant roots require for optimal growth and development. Even with the supplementation of root tabs, sand, and gravel alone are not long-term solutions for maintaining a healthy planted aquarium.⁣ By choosing an aquarium soil substrate, you will observe a noticeable and significant improvement in the health and success of your plants.

Types of Aquarium Substrates

There exists so many different sizes, shapes, and colors of substrates to choose from for your planted aquarium, but most fall under three types: gravel, sand, and soil. This section will go over each of their strengths and weaknesses. 

Gravel

Gravel is a popular substrate choice in aquariums as it offers a range of sizes and styles to suit different preferences. It is often favored by beginner aquarists due to its affordability and versatility. Gravel can provide a natural look to the aquarium, with various types of stones mimicking the appearance of riverbeds or natural habitats. Additionally, artificial gravel options are available in vibrant colors, allowing for creative and colorful tank setups.

• Important: some types of gravel can have sharp and jagged edges, which pose a risk to bottom-feeding fish. These fish, while foraging for food, may come into contact with the sharp stones and potentially injure themselves. Cuts and injuries can lead to bacterial infections, jeopardizing the health and well-being of the fish. To ensure the safety of bottom-dwelling fish, it is advisable to choose round gravel that lacks sharp edges.
  

One benefit of using gravel as a substrate in the aquarium is its compatibility with live aquatic plants. With the addition of root tabs, plants can be securely planted in the gravel, providing stability and anchorage. Although gravel may not provide essential minerals for optimal plant growth, it allows for the spreading of plant roots throughout the aquarium substrate.

Another advantage of gravel is its inert nature, meaning it does not alter the water parameters of the aquarium. This can be preferred by hobbyists who want to maintain stable water conditions and have more control over the tank's parameters.

Sand

Sand, a finer and softer substrate compared to gravel, consists of tiny particles of rocks, shells, and other materials. It is particularly suitable for bottom-feeding fish or those with soft bellies due to its fine texture and gentle feel.

Although the color variety may not be as extensive as gravel, there are still options available in different colors and sizes. Popular choices include white, black, and light brown. For a more natural appearance, beige-toned natural sand is available in two granule sizes.

One advantage of sand is that debris tends to stay on top of the compacted surface, making it easy to clean by simply using a siphon to remove the debris. However, caution is needed during siphoning to avoid inadvertently removing sand along with the detritus. It may be necessary to add more sand to fill in any areas that become exposed after each water change.

It's important to be mindful that sand can occasionally be stirred up in the water, potentially causing damage to filters and pumps if it gets sucked into the equipment. Careful pouring of water during water changes can help minimize this issue.

Due to its compact nature, sand may pose challenges for keeping live plants. The density of sand can inhibit proper root growth and spread, and it does not provide nutrients for plants. Therefore, it is not the most suitable substrate for a planted aquarium, even with the use of root tabs.

Additionally, the compactness of sand can lead to the formation of anaerobic areas where oxygen exchange is limited. These areas can harbor bacteria that convert nitrates back into ammonia, which is toxic to fish.

• To address potential anaerobic areas, options include using a thinner layer of sand, having bottom-feeding fish sift through the sand regularly, or manually sifting the sand during maintenance to promote better water circulation.

Soil

Aquarium soil is a nutrient-rich clay-based substrate that greatly benefits plant growth in aquariums. It is the top choice for high-tech planted tanks and provides optimal conditions for plants that primarily absorb nutrients through their roots.

Compared to other substrates, aquarium soil has limited variation in size and color. The granules are typically large enough to allow water flow, providing ample surface area for beneficial bacteria to colonize and support the nitrogen cycle in the tank.

• Hint: It is recommended to have a substrate depth of at least 1.5 inches (4 cm) for optimal root growth when using aquarium soil.

This active substrate influences the water chemistry by lowering the pH and softening the water, creating favorable conditions for tropical fish and shrimp. However, the reduced mineral content may not be suitable for live-bearers like guppies, which require higher mineral levels. To address this, additional minerals can be manually added during water changes or a substrate like crushed coral can be used to gradually release minerals into the water over time.

It's important to note that some aquarium soils may initially release ammonia into the water after being added. This can be problematic in newly established tanks, causing ammonia spikes that are harmful to livestock and promote algae growth. Algae is considered unsightly, and most aquarists strive to prevent its presence in their aquariums.  Learn more about algae in the planted aquarium by clicking here.

Over time, aquarium soil becomes depleted of nutrients. It is advisable to supplement the soil with root tabs after a year or two to replenish the nutrient content and support continued plant health and growth.

Best of All Worlds

The beauty of aquascaping lies in the freedom to combine multiple substrates in an aquarium. There are no strict rules dictating the use of only one substrate type.

In fact, it is quite common to incorporate different substrates to achieve the desired aesthetic and functionality. For instance, if you prefer a clean and bright look with visible sand, but also want to create a lushly planted tank, you can use a combination of soil and sand. Placing the nutrient-rich soil at the back of the tank allows plants to thrive, while the sand can be used in the foreground for a visually appealing effect.

To prevent the substrates from mixing over time, it is advisable to use rocks or other decorative elements as barriers between them. Some aquascapers even utilize gravel around the rocks to create the illusion of depth, incorporating all three main substrate types into their design.

Designing the layout of an aquarium is akin to creating a work of art, allowing for endless creativity and personal expression. As long as you have the necessary materials, you can explore and experiment with different substrates to achieve your desired aesthetic and functionality. With this foundational knowledge of substrates, you can confidently embark on your aquascaping journey. Happy scaping!