Flourite® Dark

  • Premium natural gravel for the planted aquarium
  • Good for the life of the aquarium
  • Rinse right in the bag (3.5 kg only)


Flourite® Dark is a specially fracted stable porous clay gravel for the natural planted aquarium. Its appearance is best suited to planted aquaria, but may be used in any freshwater aquarium environment. Flourite® Dark is most effective when used alone as an integral substrate bed, but it may be mixed with other gravels. Gravel modifiers such as laterite are not necessary. Flourite® Dark is not chemically coated or treated and will not alter the pH of the water. Flourite® Dark is good for the life of the aquarium and need not be replaced.

To determine the number of bags required for your aquarium, please note that each bag (7 kg, 15.4 lbs) occupies a volume of approximately 5,500 cm3 (325 cu. in.). To determine your desired volume multiply tank width by length by desired depth.


Although it is pre-washed, because Flourite® Dark is a natural product, it may become dusty in transit and require rinsing before use to remove any residual dust.

NOTE: The specialized mesh bottom of the 3.5 kg size allows it to be rinsed right in the bag.

TIPS: When adding water to aquarium, fill slowly to avoid disturbing Flourite® Dark substrate bed. Place a bowl in the aquarium and add water directly to the bowl, allowing water to overflow softly on to the gravel bed. Initial cloudiness is normal. To remove cloudiness, use mechanical filtration (such as filter floss). Clarity™ clearing. For an even stronger root zone and enhanced growth rates, add a 2.5 cm (1 inch) base layer of Onyx Sand™ to your aquarium before adding Flourite® Dark.


3.5 kg, 7 kg

Mineral Composition

Aluminum 2,166
Barium 3
Calcium 2,378
Cobalt 2
Chromium 5
Copper 11
Iron 5,326
Potassium 136
Magnesium 2,422
Manganese 384
Sodium 269
Nickel 3
Vanadium 3
Zinc 60

Units=mg/kg, source: Plasma Emission Spectrometer, EPA Method 6010, Univ. of Georgia Chemical Analysis Lab

Wondering how many bags you will need for your project? It's easy to figure out with this gravel calculator. Just enter the length and width of your aquarium along with the desired depth of the substrate and click calculate. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.

You require:

7 kg bag(s) or 3.5 kg bag(s)

A: Flourite inherently contains only micro nutrients and these are slowly released, many not released unless actively transported by the plant roots. Thus the substrate should be self-sustaining for many years and should never actually require replacement.

A: Depending on how dense the growth or how dense you wish it to be, the use of Flourish,(foliar feeding), Flourish Tabs (root feeding) and Flourish Iron can be useful and helpful beyond the substrate itself, but are not necessities.

A: Flourite will work fine with an UGF. Flourite is ideally sized and has a clay based composition (including minerals such as iron and manganese) that is ideal for plant growth. Flourite will not soften or decompose to an unsuitable state. In addition, Flourite has an attractive, natural appearance.

A: It is possible to experience an excess of particles/dust from this product due to frictional action in packaging and shipping. Flourite Red is an ore with a rich mineral composition and is not chemically coated. Even though some small particles washed away, the product is completely viable and will still offer the same benefit. A better way to add this to an established aquarium is to add small amounts at a time a half day to 24 hours apart making sure these small amounts are rinsed thoroughly. You can also use a water clarifier like our Clarity to clump any small free floating particles together making it easier for your mechanical filter to catch. Your cartridges/floss will tend to clog from all the particles being trapped and will need rinsing or replacing regularly.

A: Flourite will not break down under long term aquarium use. Though it is a fracted clay based substrate, this clay is as hard as a rock - not soft. For all intents and purposes, it is a rock. This substrate is made up of a rich mineral composition, not just coated with a fertilizer so your plants will derive a long term benefit from this substrate.

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3733 Flourite Dark 3.5 kg
3735 Flourite Dark 7 kg