Pro Shrimp's comment: Mineral stones keep releasing
minerals into the water (constant low amounts, which do not affect the
water parameters by much), supplying bacteria and microfauna with a
constant stream of needed minerals. Additionally these stones can absorb
toxins and polutants via ion exchange, thus improving water quality
directly and indirectly. We have these stones in most of our tanks.
Shrimps love to graze on these stones. From time to time it's advised to
give the stones a little clean with an old toothbrush to remove algae.
Benefits
Helps maintain good water quality by absorbing harmful waste
Enhances the colour of shrimp and fish, especially whiteness