Choosing the right substrate is one of the most common challenges beginner aquarists face. With so many options, it can be tough to make the right call. For instance, is gravel better than sand? Do some fish or amphibians do better with larger pebbles or fine stones? Do quarantine tanks and tubs even need substrate?
There are many factors that will guide you toward the right substrate for your aquarium. Taking a few moments to consider the elements below can help you make a well-informed decision.
1. Understand the Different Substrate Types
Before you can choose the right substrate for your aquarium, it’s important to understand the different types of substrates and their benefits. For example:
- Sand is best for aquariums with burrowing fish, like goby and loaches. It also adds a visual appeal to many saltwater tanks.
- Gravel is the most common substrate in many freshwater aquariums. It’s fairly easy to clean with a gravel cleaner (a siphon that sucks away debris), and the centimeter-sized stones are great for anchoring slow-growing aquatic plants, like java ferns.
- Clay is easily compacted and is ideal for aquarists who are more focused on keeping underwater plants than fish. The tightness of clay keeps root systems in place, which is conducive to plant growth.
- Aragonite and other calcium-rich substrate is ideal if you’re keeping a saltwater aquarium. They will not alter the water’s pH, keeping the levels at around 8.2 to 8.4.
Every aquarium keeper should also have a back-up tank that they use when cleaning the aquarium or isolating sick fish. Here, a substrate isn’t needed; there’s nothing wrong with using a bare-bottomed tank for temporary housing.
2. Consider the Animals You Want to Keep
The type of marine life you want to keep should play a primary role when choosing the right substrate for your aquarium. As noted, sand is a good call if you’re keeping burrowing fish and bottom feeders, such as pleco and cory catfish. A note: while sand makes a great substrate, it can easily cause clogs if it gets kicked into the filtration system. You may pair a sandy-bottomed aquarium with a strong filter to prevent this from happening. A clogged filter will lead to a cloudy fish tank and potentially throw off the water parameters.
Gravel is great for aquariums with top-water fish, such as betta fish, tetras, and danios. It’s not suitable for axolotls, as these smiley-faced amphibians will eat anything that fits in their mouths. Even a small piece of gravel could cause an obstruction and warrant a trip to the emergency vet. Sandy and bare-bottomed tanks are recommended by many experienced axolotl keepers.
Crushed coral and aragonite are recommended for fish that require a higher pH than others. These substrates keep the water “hard” and create ideal environments for African cichlids.
3. Think About Whether You’ll Add Aquatic Plants
Right now, your focus may be on setting up a new aquarium and establishing a home for new fish. However, down the road, you may decide to introduce some plants that not only provide oxygenation to the water, but also provide enrichment and hiding places for your pets. For freshwater tanks, java ferns, Amazon sword, and Anubias plants are great. Owners of saltwater tanks may turn to finger algae, brush plants, or fan plants.
For your plants to thrive, they’ll need a firm substrate that allows them to extend their roots and remain anchored. Many aquarists recommend using a mix of sand and soil for this purpose. When setting up your tank, spread some soil a few inches deep, then cap it using sand. This will keep the soil from mixing with the water and encourage it to settle.
Note that over time, the soil and the sand will mix, which may affect the tank’s aesthetic. You may consider purchasing soil specifically made for aquarium use rather than using dirt from your garden. This specially made soil is less likely to mix with the water and may settle easily to the tank’s bottom.
4. Evaluate Your Tank Cleaning Habits
There’s no getting around it: as inconveniencing as it may be, you must regularly clean your aquarium. This involves scrubbing tank decorations, changing the filter, and conducting partial water changes. You may also have to clean the substrate. Cleaning a gravel-bottomed or coral-bottomed tank is easy. There are many siphons made for this purpose. Using a wide cylinder, these mechanisms suck up water and filter out uneaten food, fish waste, and other debris trapped between the gravel. It’s straightforward to use, and it likely won’t disturb the fish in the aquarium.
Cleaning sandy substrate can be more of a headache, but it’s not complicated. Using a handheld garden shovel, scoop the sand into a bucket. Then, blast the sand with a hose, and with a strainer, separate the sand from the dirty water.
Everybody has their own process for maintaining a healthy and balanced aquarium. There are many people in the aquarium community who are eager to share their knowledge and “hacks” for maintaining underwater ecosystems.
5. Experiment With Different Substrate Types
Feel free to experiment with different types of substrates when choosing the best one for your aquarium. You can do this by purchasing small plastic aquariums (like the ones used for tubbing axolotls), laying a few inches of substrate, and filling them with water. During this trial-and-error experimentation, ask yourself:
- How long does it take for the substrate to settle to the tank’s bottom?
- Is there a cost-benefit analysis that could influence your decision?
- Is one type of substrate more easily disturbed than another?
- Is your aquarium’s filtration system compatible with a particular substrate?
- Will this substrate help maintain a clean and healthy aquarium?
Remember: your goal is an aquarium-keeper is to replicate your pet’s natural environment to the best of your ability, whether this involves purchasing gravel, sand, or a calcium-rich mixture.
