Aquarium substrate serves many purposes, from helping to control water chemistry to providing a home for beneficial bacteria. It can also enhance fish color and add to the aesthetic of a tank.
The type of substrate you choose really depends on what kind of fish you’re planning to keep and the kind of flow in your tank.
Tank Substrate Options
When it comes to tank substrate there are plenty of options out there. The largest type of substrate used is gravels or pebbles which come in a wide variety of sizes and colors. Some are even made of glow in the dark plastic. Often these are used in conjunction with other materials like clay, crushed shell and ADA’s Aqua Soil to create unique and eye-catching aquascapes.
Other popular gravels include lava rock and lava cobble which can be used to create a volcanic look in the aquarium. Crushed shell has also found some favor with hobbyists owing to its similarity in appearance to a natural stone beach. It is also known to raise the pH and KH levels in the water. Clay has a very high cation exchange capacity (CEC) and is great for supporting bacterial colonies and providing a medium for plants to take root.
Seachem Flourite Black is a very fine black textured product that has a lower concentration of Iron than regular Flourite allowing it to be used in tanks with barbels and other fish that require a low level of Iron. It has the same nutrient content as regular Flourite making it ideal for planted tanks. Another great option for those without a nutrient-rich substrate is API’s Root Tabs which are classic pill shaped products that contain nitrogen, phosphorous and potassium as well as trace elements.
Best Substrate for Planted Tanks
For planted tanks soil is a great option. It provides a nutrient-rich surface for roots to grow into. It can also help anchor plants down in the tank. It’s generally easy to find in a wide variety of colors and sizes to suit many different set bo cuc be ca canh aquarium layouts.
Some plant enthusiasts use a mix of soil and gravel. This gives the aquarium a unique look and can be aesthetically pleasing. Soil typically has a higher CEC than sand. CEC is like a very SMALL bank account for your plants that store nutrients until the plant can use them. Soil can be expensive but is usually worth the extra cost.
Some popular soils include Fluval Stratum, Seachem Flourite Black, and CaribSea Eco-Complete. One disadvantage to some of these products is that they are often sterilized which can deplete the soil of beneficial organisms. In addition, the baked clay that these substrates are made from loses some of its CEC. This makes them less useful for a planted aquarium where a aquarist is regularly fertilizing the tank.
Freshwater Tank Gravel vs. Sand
The choice between sand or gravel for freshwater planted tanks depends on the type of fish and plants that are to be kept. Gravel is suitable for most freshwater animals and does not change water chemistry, making it easy to clean. It also encourages beneficial bacteria and microorganisms that help to break down waste, thereby aiding biological filtration.
However, large gravel grains can clog filters and are difficult to vacuum, so frequent cleaning is necessary. The gaps between gravel particles allow debris to collect which can quickly rot and release toxic substances. This is particularly a problem with bogwood and driftwood that can release cyanide in the process of decomposition.
Alternatively, you can use artificial aquarium gravel made from silica or industrial resin and sealed to retain its colour. This looks very much like natural gravel, requires little rinsing before use and is available in a wide range of colours and shapes. However, it does not promote the growth of healthy bacteria and may not be as good for aeration as sand. It also has a limited capacity to hold nutrients for plant roots so you will need to supplement with liquid fertlizers.
Marine Tank Substrate Choices
When it comes to marine aquarium substrate, there are a wide range of options. Unlike planted tank gravel, which is often chosen purely for aesthetic purposes, the substrate material you choose can have an impact on water quality, habitat and the well-being of your marine species.
One popular marine aquarium substrate is crushed coral (CC). Comprised of small, crushed skeletons and shells, CS is not only visually appealing but has several key functions. For example, it helps to buffer calcium and alkalinity levels while also providing a medium for beneficial bacteria colonies to grow.
Another popular choice is aragonite sand. Made from ground-up crystalline forms of calcium carbonate, aragonite is similar to CC in that it helps to buffer pH and alkalinity levels while providing an excellent medium for beneficial bacteria colony growth and coralline algae development. It also has the added benefit of being slightly heavier than sand and thus less likely to be blown around by the water flow in your reef tank. This makes aragonite a good choice for deep bed tanks and aquariums that house sand-dwelling creatures such as sifting gobies or wrasse species.
Choosing Substrate for Terrariums
Choosing the right substrate is a highly personal choice, ranging from neon pink gravel to match a castle or mermaid theme for children’s aquariums to a natural brown gravel that complements driftwood, rocks and live plants. Generally speaking, a dark color is preferable for a fish tank because it makes light-colored fish stand out while a bright substrate can easily wash out the colors of darker fish.
Adding an admixture like perlite or vermiculite to a terrarium soil mix increases drainage, aeration and permeability. It also helps keep the soil loose and reduces soil compaction that inhibits root growth. In addition, these lightweight materials bind to terrarium contaminants and remove them from the water.
Suitable terrarium substrates also allow for burrowing behavior, egg deposition and hiding places. For example, good ol’ cypress mulch is a popular option for terrariums that house bearded dragons, leopard geckos and fat-tailed geckos because it retains moisture and doesn’t splinter. Other suitable terrarium substrates include stone desert, plantation soil and forest moss.