Active substrate for aquariums. Active soil influences water parameters and adjusts them to a pH range that is favorable for most aquarium plants. Nutrient reservoir: It can absorb nutrients from the water and release them back - the buffering effect is ideal for healthy plant growth. Naturally appearing grain size - ideal for small, medium, and larger aquascapes, providing good support for plant roots. Color: Black. Grain size: 2 - 4 mm. Package size: 2.7 kg.