Onyx is a specially fracted porous substrate for the aquarium, Onyx is suitable for most marine and freshwater environments including reef and planted aquariums, Onyx is most effective when used alone as an integral substrate bed, but it may be mixed with other gravels or sands, Gravel modifiers are not necessary, Onyx is not chemically coated or treated but does have a slight Buffering capacity, Although pre-washed, it should be rinsed before use to remove residual dust, Slight initial cloudiness is normal and will clear rapidly (2-12 hours), This bag is sufficient for about a 5 cm (2 inch) deep bed in a typical 10 gallon tank, Recommended use is 1kg for approximately each 200 cm2 (31 in2) of tank bottom at a depth of 5 cm (2 inches), 7 kg / 15, 4 lbs (Treats 1,400 cm2 (217 in2) at a 5 cm (2 in, ) depth), SKU: RYLHC5052