The sudden death occurrences in Arowana are caused by internal bacteria infection. Some of such occurrences do not show any symptoms at all. Special Arowana Internal Bacteria & Ulcer Away is an advance remedy to act fast against such bacteria attack and prevent it from spreading further. It is less toxic than other medication in the market. Will not dye/color the aquarium water. This medication is harmless to all fishes,filter bacteria and plants. Specially formulated for Arowana and other fishes.