Tints for ponds and pond colorants help against the growth of weeds and algae by naturally filtering UV rays of sun which cause non-desirable aquatic plants and weeds to grow. Safe for recreational ponds, fish, plants, horses, cattle, birds, fish, dogs and cats and the environment. Available in blues and black and in liquid or dry form.  Also used strictly as an aesthetic additive to add a shade of blue to brown or  muddy waters.