If you’re putting together an aquarium for the first time, you need to seriously think about substrate. This is the material that will lie at the bottom of your tank, with gravel and sand being the two most popular options when it comes to substrate. Although these two materials might seem pretty similar, each type has their own distinct advantages and drawbacks when it comes to setting up an aquarium. Some fish species do better with sand as a substrate, while many aquarium plants will in fact benefit from gravel substrate layers. Our guide breaks down the key information you need to know when selecting a suitable substrate for your aquarium.
Gravel as a Substrate
If you’re putting together a freshwater aquarium, gravel is usually the best choice of substrate material. The main benefit of gravel is that it allows tank water to more easily penetrate the substrate layer and through through it. This permeability means bacteria is less likely to gain a foothold in your substrate, preventing the need for constant cleaning and maintenance. If bacteria is allowed to colonise substrate layers for long enough, it can lead to considerable mould growth within your aquarium, which can have a huge impact on the overall health of your fish.
The bulkiness and weight of gravel also prevents your substrate material from being pulled into any filters you have installed in your aquarium. This means you will not have to worry about problematic clogging, which can impair the efficiency of filters and lead to poor aquarium water quality. Gravel is also readily available and affordable, with many grain sizes and colour options to choose from. This means you have plenty of choice when it comes to aquarium aesthetics. Aquarium owners who plan on putting together a colourful variety of tropical fish will definitely want a substrate that complements their collections.
Sand as a Substrate
Sand is nowhere near as permeable as gravel, so water has a harder time at penetrating through it. That means you may encounter more issues with bacterial build-up if your substrate layer is not properly circulated and maintained. However, a sandy substrate layer is often the preferred choice if you are keeping certain varieties of fish. If the fish in your collection are prone to natural burrowing behaviour, sand is an ideal material for the bottom of your tank. This burrowing and scavenging behaviour will also go some way in ensuring the substrate layer is kept relatively clean and free from excessive amounts of bacteria.
Sand also has several other benefits as a substrate layer that gravel doesn’t. Many people prefer the more natural aesthetics of sand as a substrate. If you’re looking to recreate an authentic riverbed environment so your fish have a fairly natural environment in which to thrive, sand is arguably your best bet in terms of a substrate material.
Provided your sand substrate has been packed tightly in place at the bottom of your tank, regular maintenance is not really something you have to worry about. If sand grains are packed together tightly enough, waste matter and uneaten food particles will usually remain on the top layer of the substrate itself, rather than penetrating more deeply before decaying. Sand is even more affordable than gravel, with many different varieties to choose from.
If you’re unsure of what variety of sand to choose for your aquarium, consider purchasing so-called live sand. This material is already partly colonised with aquatic bacteria that will benefit the internal conditions of your aquarium. If you need to replace an existing substrate layer, live sand is a particularly good choice of material as it allows for water chemistry to remain more stable. The downside of live sand is that it is considerably more expensive than other sand substrate options.
Which Substrate Should You Choose?
Although aesthetics are important when it comes to furnishing an aquarium, they should come second to practical considerations. Think about the health requirements of the fish and plants you are looking to house in your aquarium before selecting a suitable substrate. Generally speaking, a gravel substrate is better for many aquatic plant varieties. Not only does gravel prevent particles sinking to the bottom of your tank and decaying, which can often prove harmful to plants, it also makes bedding in plants far easier.
Different fish species will have different requirements when it comes to substrate material. If you’re only looking to house goldfish varieties in your aquarium, you should avoid sand material and opt for gravel instead. If sand grains are accidentally ingested by goldfish, these particles can cause blockages in their intestines. This can lead to ill health in your fish and affect their feeding behaviour.
Even if you spot the problem quickly enough, you may not have time to swap out sand for a gravel substrate before your goldfish succumb to these ill effects and perish. However, some fish species prefer sand as a substrate. In fact, certain breeds from the cichlid family use sand to aid digestion. These fish use sand particles in much the same way that larger animals use rocks as grazing stones, with the grains helping break up food in their stomachs and intestinal tracts.
There are several different gravel options you can choose as a substrate. However, the best of the bunch has to be live gravel substrate. As with live sand, this gravel already contains a certain amount of bacteria, which will provide your aquarium with essential nutrients and help ensure stable water chemistry if you are replacing substrate layers in their entirety. Unlike other forms of gravel, live gravel can also be added as is, with no rinsing or preparation required. There are some drawbacks to live gravel substrate, however. For starters, you’re quite limited when it comes to colour and size options. What’s more, live gravel is considerably more expensive than standard substrate material.
Adding Substrate to an Aquarium
Regardless of whether you opt for sand or gravel as a substrate, you should make sure you are using the correct amount of material for your size of tank. If you have a smaller aquarium, the substrate layer never needs to be more than three inches deep. If you larger aquarium, you will need to add at least another layer of material. There’s no strict rule on how frequently you should be looking to replace substrate material. Ultimately, you should judge the condition of your substrate by eye before deciding on whether it needs to be replaced. If the substrate layer has accumulated a lot of bacterial growth or gravel looks muddy, it is almost certainly time to replace it.
If you’re looking to make long-term savings, gravel is a better choice of substrate material as it can be more easily cleaned and reused. Even a thick layer of slime can be rinsed away with relatively little effort before being returned to the tank. By contrast, sand is much harder to rinse, so you will almost certainly need to replace a sandy substrate layer with fresh material.
The Verdict
Sand and gravel each have their own unique benefits, but both can be used effectively in most freshwater aquariums. Go for sand as a substrate if you’re looking for a natural aesthetic and have a collection of fish that exhibit burrowing and scavenging behaviour. Although sand is suitable for use in tanks that use canister and hanging filters, you will still want to keep an eye out for clogs and impaired filter performance.There are some downsides to using sand, however. It can quickly become disturbed, leaving the bottom of your tank looking unsightly, which will require regular maintenance. Aquatic plants will also struggle to thrive in a tank with a sandy substrate.
Gravel is the go-to choice of substrate material if you prefer the appearance of a tidy tank. It is also the best option for those who want to incorporate thriving aquatic plants in their fish tanks. You will however need to ensure you are using a specific type of filter if you are using gravel as a substrate. Any tank filter will need to be placed beneath the substrate layer itself. Gravel is also far easier to maintain. You can more easily rinse and clean gravel for repeated use, while the substrate tends to be more accommodating to a wider variety of fish and plant species.
