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Home > General > Seachem Flourite Black Sand Review: Our Fish Expert’s Opinion

Seachem Flourite Black Sand Review: Our Fish Expert’s Opinion

Seachem Flourite Black Sand - Featured Image

Review Summary

Our Final Verdict

We give Seachem Flourite Black Sand a rating of 4.5 out of 5 stars.

Quality: 4.5/5
Functionality: 4.5/5

What Is Seachem Flourite Black Sand? How Does It Work?

If you’re looking for a high-quality, inert substrate for your planted tank, then the Seachem Flourite Black Sand may be your dream product. This highly porous substrate consists of tiny pieces of inert clay that are similar to coarse sand. The texture and size of the pieces allow for excellent root expansion for plants. It is heavy enough for plants to grip and to hold them in place while they are rooting, but it’s not heavy enough to weigh down plant roots and limit growth. The biggest downside of this product, though, is that it does not include anything that will support plant growth, so you will likely need to use it in conjunction with fertilizer and root tabs.

Unlike many substrates intended for planted tanks, this substrate does not alter the pH of your water. This allows you plenty of control over your water’s pH and won’t make it difficult for you to raise or lower the pH. Since it’s made from porous clay, it features an extremely high surface area, which supports the colonization of beneficial bacteria that are necessary to maintaining a healthy tank. It is not chemically coated or treated, so there are no chemicals in this product that will leach into your tank.

Seachem is a trusted name in the aquatics community. They produce products for tank care and maintenance, like water treatments and fertilizers, products that support the health and wellness of your aquatic animals, like medications, and tank-related products, like substrates. Seachem is a US-based company that has been in the business for over 40 years and sells products in over 60 countries. They are leaders in producing high-quality products for the healthiest and most attractive aquariums.


Seachem Flourite Black Sand – A Quick Look

Seachem Fluorite Black Sand

  • Inert
  • High surface area
  • Great for planted tanks
  • Lasts for the life of your tank
  • Not coated or treated

  • Contains a lot of dust if not thoroughly rinsed
  • Does not contain fertilizer or other growth supporting chemicals

Seachem Flourite Black Sand Pricing

When it comes to buying aquarium substrate, the Seachem Flourite Black Sand is moderately priced. It routinely goes on sale, though, so you can often pick it up at a discounted price. With normal pricing, you can expect to spend about $2-3 per pound. The size of your tank and preferred depth of substrate will determine how much you need to purchase. The general recommendation is a pound of substrate for every gallon of tank size. This will give you between 1-2 inches of substrate depth.

Seachem Fluorite Sand Black

What to Expect from Seachem Flourite Black Sand

Seachem Flourite Black Sand is an attractive, clay-based substrate that is ideal for planting tanks and maintaining colonies of beneficial bacteria with its high surface area. This substrate is described as gravel, but it is similar in texture and size to coarse sand. It is made from porous clay and is intended to last for the life of your tank without requiring replacement. It’s intended for use in planted freshwater tanks and the manufacturer recommends using it on its own, but Seachem Flourite Black Sand can be mixed with other gravel-type substrates if preferred.

Seachem Flourite Black Sand Contents

  • Made from specially fracted porous clay
  • Stable and inert ingredients
  • Not coated or treated
  • High surface area
  • 7-pound and 15.4 pound bags are available

Product Quality

Like all Seachem products, the Seachem Flourite Black Sand is high-quality and safe. It’s made to never need to be replaced, so it’s sturdy and will not leach color or chemicals into the water. It can also be washed and disinfected if needed to set up a new tank or treat severe disease in your tank. The high surface area of each piece ensures your tank will be thoroughly colonized by beneficial bacteria.


Seachem Flourite Black Sand is one of the best products on the market for planted tanks. It provides the perfect size, weight, and texture to support plant growth and root expansion. Since it is fully inert, it allows you to alter the pH of your tank as needed to support the specific plants you are keeping. It will retain its color for a lifetime and won’t discolor your tank if it is rinsed thoroughly before use. Also, since it’s bigger than sand but smaller than normal gravel, it allows you to thoroughly clean your substrate, which can be difficult with regular sand, while encouraging plant growth, which can be difficult with gravel.

Why Ingredients Matter

Choosing an inert substance as the singular ingredient of this product ensures that you have full control of your water parameters. You won’t be fighting against a substrate that naturally raises or lowers pH or impacts other water parameters. Since it’s a naturally occurring substance, the color is natural, so you will not end up with black dye leaching into your tank.


One downside to the Seachem Flourite Black Sand is that, although it’s intended for planted tanks, it doesn’t include any products to stimulate or assist the growth of plants. This means that root feeders will likely require root tabs under the substrate to provide them with adequate nutrients. On its own, this substrate will not feed your plants.

It’s also important to note that, since this is a natural product, it has quite a bit of dust. It should be thoroughly rinsed before use and does not come pre-rinsed. If not rinsed thoroughly, you may have to work to remove dust from the water until everything settles.

Is Seachem Flourite Black Sand a Good Value?

If you’re adding substrate to your planted tank, this is a good value since you will never need to replace it. It can be an expensive up-front expense but will last a lifetime. Another factor influencing the value of the product is that it’s intended for planted tanks but lacks fertilizers, so you will need to invest in fertilizers and root tabs separately.


FAQ: Seachem Flourite Black Sand

Will this affect the hardness or alkalinity of my water?

No, Seachem Flourite Black Sand won’t alter the GH or KH of your water due to its inert nature and lack of additives.

Is this shimmery or matte?

This substrate has a matte finish.

Is this safe for scaleless and soft-belly fish like Kuhli loaches and Corydoras?

Yes, this is safe for soft-belly fish and invertebrates like snails.

Can I add this straight to my tank without rinsing it?

While you can do this, it’s not recommended. If you add this substrate to your tank without thoroughly rinsing, you will be fighting cloudy water for days, if not weeks.

What the Users Say

For anyone who wants more opinions than just our expert’s, we’ve rounded up what other people who have used this substrate are saying about it. Many people find that this substrate reduces the difficulty of their tank cleaning and maintenance when compared to regular gravel or sand. This is only the case for people who thoroughly rinse the product, though! Users who have added the substrate to their tank without rinsing it have found it to create cloudiness for at least a few weeks after putting it into the tank when adding plants, doing water changes, and any other tasks that stir up the substrate.

Many people who have used this substrate feel it’s the best substrate for planted aquariums. This is because it doesn’t alter water parameters, is safe for fish and invertebrates, and creates a healthy environment for plants that allows you to choose your preferred fertilizers and plant food. Root tabs are a must for root feeders when using this substrate, though.



Seachem Flourite Black Sand is the best option if you’re looking for a dark substrate that helps support a healthy planted tank. It provides just enough customization without leaving you overthinking or worrying about the well-being of your plants and animals. It’s inert, never requires replacement, and can even be used with under gravel filters. The coarse, silty texture is plant-friendly and won’t harm even the most delicate of your aquarium inhabitants.

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