ultum nature controsoil freshwater planted aquarium substrate - extra fine black (3 liter)  ultum nature systems controsoil is an aquarium soil from japan made of high-quality natural soil and volcanic ash. choosing a proper substrate is vital for any successful planted aquarium. this is not only for aquarium plants to flourish but also to buffer the water to optimum levels for certain fish and shrimp. controsoil by uns will keep the ph of alkaline water below 7 which is ideal for keeping caridina shrimp and most tropical fish.