Organic soil, sand and gravel are the cheapest aquarium substrates that can be used for both planted and unplanted tanks. A combination of organic soil and sand will promote the best plant growth. Sand on its own is likely the least expensive.
The following table shows some of the cheapest aquarium substrates by volume.
|Substrate brand||Price (USD)||Price per cubic inch (USD)|
|Kellogg Organic Plus Potting Mix (2,990 cubic inches)||$8.97||$0.003|
|Nature’s Care Organic and Natural Potting Mix (718 cubic inches)||$11.49||$0.016|
|Imagitarium River Rock Shallow Creek Aquarium Gravel (400 cubic inches)||$19.54||$0.049|
|CaribSea Super Naturals Sand (189 cubic inches)||$10.99||$0.058|
The table above is not an exhaustive list. There are many brands of organic soil, sand and gravel that have comparable prices to the list above.
Soil, gravel and sand are substantially cheaper by volume than commercial aquasoils or some aquarium-specific inert substrates.
Cheapest substrate for heavily planted tanks
The cheapest planted aquarium substrate by volume is organic soil capped with sand. However, both of these substrates are often sold in large volumes, which may end up costing more overall if you are only using it for a small aquarium.
A sand or gravel-only substrate would likely be the least expensive option in this case because you would only have to buy one bag. However, neither sand nor gravel are great solo options for heavily planted tanks.
For heavily planted tanks, we recommend an organic soil that’s capped with sand or a commercial aquasoil.
Why is organic soil the cheapest aquarium substrate?
Organic soils are harvested more easily in large volume than other inert substrates such as sand or gravel. Commercial planted aquasoils undergo a manufacturing process to achieve the right formula and grain size. This adds to their cost.
Organic soils are also manufactured at a much larger volume for home gardening and landscaping needs. This large scale production has helped bring prices down as well.
Can you use garden soil in an aquarium?
It’s important that you only use organic top soil, organic potting mix, or organic potting soil. This ensures no chemicals or other artificial additives are mixed into the soil.
Organic soils often contain added organic fertilizers such as bone meal, earthworm castings and manure. These organic fertilizers are perfectly safe for an aquarium. In fact, they are tremendously beneficial for promoting excellent plant growth.
You have to cover your organic soil with a layer of sand or fine gravel to ensure it doesn’t leech into the water column and make it cloudy.
Can I grow plants in sand or gravel?
It’s certainly possible to grow aquarium plants in sand or gravel. However, these inert substrates will not provide adequate root nutrition and will require regular root tab fertilization to promote healthy plant growth.
We recommend using a base layer of organic soil or an active aquasoil if you’re planning on building a planted tank though. This will give your plants the best chance at success.
Where to buy cheap aquarium substrate
Local fish stores will sell inexpensive sand and gravel
Most local pet stores or specialty aquarium stores will carry several brands of gravel and sand. These are the most popular types of substrate sold to the average aquarist.
You will likely be able to find an inexpensive option that suits your tank’s style.
Sand and gravel can be bought online from Amazon
There are many sands and gravels available online. We recommend choosing one with a high average customer rating and many reviews.
Organic soil can be bought from a local nursery or garden store
The best place to buy organic garden soils is from a local nursery. They will often sell their own brand of organic soils.
Another great place to check is The Home Depot, Lowe’s or Walmart. These big box superstores have a good selection of organic potting mixes online, which can be purchased from most local stores as well.
It might be worth calling your local store or viewing their online inventory to make sure they have the right soil in stock before dropping in.