Can You Use Pool Filter Sand as Aquarium Substrate?

Pool Filter Sand

Pool filter sand

Pool filter sand is not the first thing that you may think about when setting up an aquarium.  There’s a fair number of things you’ll need to buy to set-up your first aquarium, and one surprisingly pricey component are the gravels and sands made especially for the bottom of a fish tank. Are there safe alternatives to these specialty products?

Sandy-bottomed tanks are a very popular trend recently, and since aquatic sands typically cost a few dollars more per pound than gravel, many budget-minded folks have asked me if they can use pool filter sand in their tanks instead.

This can be a viable option, so let’s take a look at the benefits and disadvantages of using pool sand in the bottom of your aquarium.

Role of Substrate in Aquariums

Before we delve into the pros and cons of using pool filter sand, let’s take a second to talk about the function of substrate and the role it plays in your aquarium’s health.

While it’s obviously a key component in your tank’s appearance, your choice of substrate also has a direct impact on the water chemistry, potential plant growth and even the wellbeing of the animals in your tank:

  • Substrates support the growth of the “good” aquatic bacterial colonies that help regulate your tank’s Nitrogen Cycle and break toxic ammonia and nitrites into safer (but not safe) nitrates
  • Your substrate also provides anchorage for live plants and supports root growth and their uptake of vital nutrients and minerals
  • Bottom dwellers often enjoy digging and hiding in it, so it’s important that your substrate is safe for these delicate fish and invertebrates if you’re planning on keeping them

Challenges of Using Sand Substrates in Aquariums

Sand can be a bit trickier to manage as a substrate than using aquarium gravels for a few reasons. Gravel has long been considered the ideal for most freshwater tanks, and especially planted aquariums, because it doesn’t compact down as much as sand, which has a few implications for your tank:

  • It takes more sand (per pound) than gravel to fill your tank to the desired depth, which may increase the costs of starting up your tank unless you opt for a less-expensive pool filter sand
  • Gravel allows more water movement through the substrate than sand, since the particles are larger
    • Sandy tanks often have problems with hypoxic dead zones, which can lead to algae blooms and eventually dead plants and animals
    • Gravel usually provides better support for live plants, since the water flowing through the substrate delivers nutrients and carries away toxins that could stunt their growth
  • Unlike gravel, fine sand particles may be easily sucked up by your aquarium filter’s intake tube or when vacuuming your gravel during routine maintenance
    • You might invest in the best filter for a 10 gallon tank, only to discover a few weeks later that sand has infiltrated the impeller and caused damage to the motor
    • If you opt for a sandy substrate, you’ll need to protect your filtration system with a pre-filter sponge tip and use a gravel vacuum with a finer screen so you don’t lose too much substrate during water changes

Benefits of Sand as Aquarium Substrate

While sand can have its challenges as a substrate, it also provides a few benefits that make it the best choice for some aquariums. Freshwater invertebrates like Cherry and Ghost shrimp prefer fine substrates like sand, and bottom-feeding fish like Cory Cats and loaches may be injured by digging through harsh aquarium gravels.

A layer of sand may also help keep your tank tidier, because debris is less likely to sink through the fine particles. They’ll collect on top of the sand instead. It’ll be easier for your filtration system to grab the debris and remove them before they begin to decay.

Making Sand Substrates Work For Your Tank

It’s not hard to manage a sandy-bottomed tank once you know the challenges you’ll face; it’s far more problematic to discover these problems in an established tank! As I mentioned above, simply using a pre-filter sponge tip can prevent the sand from being ingested into your filter.

It’s harder to increase the water flow through a fine sand substrate, but there are still a few things you can do to prevent oxygen depletion in a tank with sand and help live plants thrive despite the sand’s natural compaction and lack of nutrients.

I often hide a layer of high-quality plant gravel underneath an upper layer of sand, which increases water circulation through the root zone and provides the nutrients and minerals live plants need to thrive. Placing a hidden layer of gravel under sand may also help prevent dead zones in your substrate, especially if you also use an air stone to increase the oxygen in your water and improve the circulation in the tank.

Pool Filter Sand vs Aquarium Sands

There’s a variety of specialty and generic sand products available online and in stores, and each type of product has its ups and downsides when used as an aquarium substrate.  Let’s briefly compare pool filter sand to these other products.

Pool Filter Sand

Pool sand is used in large swimming pools and spa filters to screen out dirt, hair/fur, oils and other debris that could contaminate the water. There’s a range of products for swimming pool filters, and not all types of pool sand are safe to use in an aquarium. Some products contain chlorine or other additives that are beneficial to swimming pools but could poison your tank and kill your fish and plants.

If you opt for using an inexpensive pool sand as a substrate in your tank, look for products labeled as quartz or silica-based sands with no additional additives.

You may find it’s cheaper to buy directly from your local pool supply shop, as they often sell basic pool sand for just a few dollars a pound and you won’t have to pay extra for shipping the heavy package. Plus, if you tell them you’re using it in an aquarium they can confirm the products are safe, too!

  • Inert pool sands are basically identical to the more-expensive plain aquatic sands and those used in terrariums and reptile habitats, and have the same benefits and disadvantages in your tank
  • Pool filter sand comes in a range of sizes, but the ideal size for an aquarium is the #20 grade, which is coarse enough to avoid clumping but still provides a fine texture and appearance in your tank
  • These sands are usually white or a shade of beige, so it’s easy to coordinate the color with your fish and decor
  • Pool sand is an ideal option for many tanks with bottom feeding fish, shrimp, and snails, and is safe for schooling and shoaling fish as well.

Branded Aquatic Sand

There are four types of specialty aquarium sands, and pool sand is a reasonable substitute for one type, but not for all four.

An ideal but expensive option for planted freshwater aquariums is using a special plant sand made from crushed ceramics. These products provide plants with essential nutrients and minerals and help boost their growth. Pool sands lack these vital nutrients, since they’re just sand.

Sand for marine and reef tanks often contains crushed coral or calcium carbonate, which alter the aquarium’s pH and increase the water’s hardness. “Live” aquarium sands come packed in fresh or saltwater and contain living colonies of bacteria to help jump-start your tank’s nitrogen cycle. Pool sand isn’t a viable substitute for either of these products.

The final type are the plain silica-based aquarium sands, which are essentially the same thing as pool filter sand. They’re available in a wider range of colors, including bright neon and pure white or black shades, but are also substantially more expensive than pool filter sand.

Children’s Play Sand

It may be tempting to save money by buying products marketed for playgrounds and sand pits for your aquarium, especially if you’d prefer a really bright colored substrate. But play sands are too fine for use in aquariums. The sand tends to clump, and even when rinsed they often leave your water cloudy. I definitely recommend avoiding play sand, since pool filter sand is a much better option at a similar cost.

Should You Use Pool Sand in Your Aquarium?

Pool filter sand is really no more challenging to use than any other plain aquarium sand and is a lot less expensive, so there’s no reason to spend more on a branded product marketed for fish tanks unless you need a specialty substrate for your plants or coral reef. For novice or casual fish keepers, pool sand is a reasonable and budget friendly option for most freshwater tanks!

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