Which aquarium substrate to use when designing your fish tank is a very important decision, and not only for aesthetic reasons.
Aquarium substrate provides a medium for your plants to take root in, a place where some fish species can spawn, and it even harbors colonies of bacteria which are highly beneficial to your fish tank.
These days there are many types of substrate available for use depending on the type of aquarium and fish you keep – in this guide we hope to explain the differences between these substrates and help you make the right choice.
Gravel is the most commonly used aquarium substrate, it’s usually available in a wide variety of different colors and sizes, and is not very expensive. Gravel which is sold specifically for aquariums is usually treated and chemically inert – ensuring it doesn’t change the chemical composition of the water.
This type of aquarium substrate is the best substrate for harboring beneficial bacteria as they will have a larger surface area to grow on. Using gravel as the only substrate is usually enough for fish-only tanks, however for planted aquariums with lots of live plants, a mixture of gravel and a fertilizer substrate such as Laterite is usually better (with gravel being mostly the top layer.)
Gravel usually needs to be cleaned every few weeks or months depending on how many and what type of fish you’re keeping, because eventually some uneaten food and biological waste will start clogging the cracks and gaps between the gravel. It’s recommended to use a gravel vacuum and to clean only around a third of your tank at a time.
- Do not overfeed your fish. Overfeeding will result in more unconsumed food and biological waste between the gravel gaps, potentially creating a toxic environment.
- Some fish like to burrow into or sift through the gravel, make sure the gravel has no fine or jagged edges which could hurt the fish.
Sand is another popular choice as it can look beautiful and a lot of fish seem to love it. It’s also cleaner than gravel as there are no gaps or spaces for waste and food to gather in, so most of the waste will be sucked out by the filter. This usually means that aquariums with sand as a substrate require less maintenance and cleaning.
Aquatic plants can thrive in sand as well as in any other substrate, however since sand does not give out nutrients like certain types of gravel or fertilizer substrate, they often must be supplemented with root tablets.
Like gravel, sand is also available in a variety of different colors and sizes. Most fish aren’t bothered by the sand’s color so it’s mostly an aesthetic choice.
- Do not use an Under-gravel Filter with sand as your aquarium substrate because the sand will get sucked through the filter and potentially cause damage.
- Sand for freshwater and saltwater tanks are made from different materials, make sure you’re using the right kind depending on your tank. Coral sand is not suitable for most freshwater fish, for example.
Crushed Coral is not very popular for freshwater tanks, since it’s known to raise the water’s pH level to an undesirable level for most freshwater species (except most African cichlids, as they seem to like a high pH.)
For saltwater tanks, coral is probably the second most popular choice since it’s beautiful aesthetically and a lot of saltwater fish seem to enjoy the increased pH level and hardness of the water.
Crushed Coral Tips:
- Even if you do not use crushed coral as your main aquarium substrate, you can add a handful of it to your freshwater or saltwater tank if you need to raise the pH naturally, this is a great way to keep your pH level balanced.
Laterite Aquarium Substrate
Laterite is an aquarium substrate made of clay, it’s rich in iron and has a high CEC value (cation exchange capacity) which means it holds and slowly releases nutrients which are good for aquatic plants.
Although it’s not necessary to use laterite as a substrate in planted tanks since most plants tend to live just fine in gravel or sand, they will surely appreciate the extra effort and grow healthier.
- Since laterite can be quite buoyant and will sometimes float, it’s best to keep it as a lower layer under another aquarium substrate like gravel or crushed coral.