Air-breathing fish are cultured almost exclusively in water without oxygenation, which is seen as an unnecessary extra expense given the animals ability to obtain oxygen at the water surface. The most common placement of the air-breathing organ (ABO) in the circulatory system, feeds oxygenated blood into the venous return to the heart, thus protecting the heart during aquatic hypoxia. However, the subsequent branchial passage may lead to oxygen loss raising the question of the extent of benefit of the ABO to the somatic system. Further, the ABO in these fish leads to a degree of separation of the functions normally associated with the fish gill, making extrapolation of tolerance to toxins from data obtained in water breathing fish a questionable practice. Here the surprising cardiovascular layout of Pangasionodon hypophthalmus will be presented together with data on the partitioning of oxygen uptake, estimated costs of surfacing and the elevated tolerance to TAN and nitrite compared to water-breathing fish.  All physiological data point towards great potential benefits for these animals from oxygenation of the water column.