Volcanic substrate is becoming increasingly popular in aquascaping due to its nutrient-rich properties. A common question is whether it can be used alone or if it needs a layer of gravel or sand on top.

Using Volcanic Substrate Alone:

• You can use volcanic substrate as the sole substrate without negative effects.

• Benefits include supporting plants that absorb nutrients primarily through their leaves rather than roots.

• However, with strong water flow, nutrients may escape into the water column, and waste or uneaten food can get trapped in the larger gaps of the substrate.

Covering with Gravel or Sand:

• Adding a thin layer of gravel or sand enhances aesthetics and helps trap nutrients in the substrate.

• This creates a stable “soil” bed for root-feeding plants and improves nutrient availability for all plant types.

• A top layer also prevents finer particles from floating and clouding the water.

Recommendation:
For best results, use volcanic substrate as the nutrient-rich base and add a thin layer of sand or fine gravel to retain nutrients, stabilise the substrate, and improve the look of your aquarium.