PREIS Bora-Bora Sand is an extremely fine white substrate of calcium and magnesium compounds that is ideal for sea water aquaria. We recommend a depth of 2 - 3 cm. At this depth and with an adequate flow of water, detritus can be expelled and nitrate deposits are avoided in the aquarium substrate. It is also ideal for mixing for DSB filter systems. In this case, the substrate should have a depth of 8 to 20 cm. PREIS Bora Bora sand is composed of an extremely pure mineral substance that does not precipitate nitrates, phosphate or silicate. PREIS Bora Bora sand has a very high proportion of calcium and magnesium and enriches the water with carbonate hardness. After operating the aquarium for about one year you should refill with 10% Bora Bora sand. This is approximately the quantity which dissolves to form calcium, magnesium and carbonate hardness. Molluscs like tube anemones and other anemones, tubeworms, feather corals and wrasses have the habit of burying themselves in this fine Bora