For the sake of simplicity this article will address substrate choices for a freshwater, non-planted tank. Substrates are added to most aquaria principally to increase the growth of beneficial bacteria this provides. However, substrates can also have a variety of direct effects on water quality by releasing substances into the water, absorbing substances from the water, or reacting chemically with substances from other sources.
Apart from all other considerations, substrates are frequently chosen for their aesthetic qualities. Some substrates are used to alter water chemistry. Crushed coral and sand contain calcium, which will raise the carbonate hardness. Substrate may also be used as part of a biological filtration system. Beneficial bacteria colonize all aquarium surfaces that are exposed to aerated water, including the substrate.
Because the numerous particles have a high surface area, substrates are often employed in biological filtration. Some common types of filtration involving the aquarium substrate includes the under gravel filter and the deep sand bed.
Planted tanks require a substrate that will remain loose enough for plant roots to penetrate it. The substrate should be chemically inert and free of sharp edges.
Appearance is often the main focus when choosing a substrate, however there are other factors that should be considered.
Are you a beginner hobbyist? If so, your best choice would be inert small gravel, as the majority of easy-to-keep fish do not require any substrate with buffering capabilities, and it’s best to use this while you are learning to keep your water parameters proper.
What color? The possibilities are almost endless. The color you choose will impact the well-being of your fish. Some fish actually prefer a lighter or darker shade and their color will change accordingly. Again, do your research. You will be able to find something that doesn’t spook your fish and is pleasing to you also. It’s almost never a good idea to choose bright neon colors that your fish would never see in the wild.
Bare-bottomed tanks can be useful as it is very easy to see detritus and uneaten food and vacuum it up. The shiny, reflective bottom can startle your fish though.
This is not a good choice for fish that like to burrow or dig as the lack of substrate will stress them. If you choose this route, there are many ways to create the look without having actual material in the tank. Natural stone flooring can be applied in the upper part of you tank stand, giving it a natural appearance without having to vacuum around anything.
Shallower beds are easier to vacuum and keep clean. No matter what you choose, make sure you thoroughly rinse it first. Just to be safe, on your last rinse, take the water level down to the top of the substrate and add a couple drops of de-chlorinator.
The bottom line is to thoroughly research your intended fish purchases and find something that matches their requirements. You will be sure to find something that both you and your fish can enjoy for years.
The type of fish you plan to keep is a major factor in your choice. Will you keep bottom dwellers that like to burrow such as Cory and loaches? Do you prefer fish that scoot across the bottom quickly such as a Pictus cat? For these fish very smooth gravel in the range of 3.00mm to 5.00mm would be ideal. Gravel this size can also be vacuumed easily. If you prefer aquarium sand it can also be used for these types of fish. Sand can be more difficult to vacuum.