A balanced diet with enriched nucleotide that increases koi immunity with a new formula that includes bacillus subtilis natto in 2.2-Pound/Bag (12bags/carton) Small (3.5-4.0 millimeter). The people of Japan have enjoyed the health benefits of natto for over 2,000 years which is why we decided to incorporate natto into our products. Through our research, we discovered when natto is used in koi food diet, it helps to: increase immunity and health, improve digestion and water quality and also enhance growth and luster. Please feel free to contact us for more information regarding our breakthrough findings. All our products are ISO 9001 and ISO 14001 certified. Aqua Master Staple koi food improves digestion, reduces water contamination and also enhances immunity.