Which is better, fish tank volcanic rock or South American sandstone?

Volcanic rocks in fish tanks are better. Fish tank volcanic rocks refer to volcanic rocks placed in fish tanks. Volcanic rocks are glassy lava with dense pores formed by the condensation of molten magma during volcanic eruption. Its pore volume accounts for more than 50% of the rock volume, and it has good water absorption and permeability. Volcanic rocks are generally big stones, because pores can be used as living places for small fish and shrimp. South American sandstone is a stone specially used for aquarium landscaping, which has poor water absorption and permeability, and is completely closed and very small, so it is better to use aquarium volcanic rock.