Gas bubble disease in fish is caused by too much which gas?

• A. Nitrogen
• B. Hydrogen sulfide
• C. Oxygen
• D. Ammonia

Answer: (A)

Gas bubble disease happens when water is supersaturated with dissolved gases, so gas bubbles form inside fish tissues and in the bloodstream as the fish navigate or as pressure changes occur. The gas most commonly responsible is nitrogen because it is the major inert component that tends to form bubbles when dissolved in water under oversaturation conditions, such as during rapid aeration, pumping, or sudden decompression in hatchery systems. These nitrogen bubbles interfere with circulation and tissue function, leading to the observed symptoms.

Ammonia and hydrogen sulfide are toxic dissolved compounds that cause chemical damage, especially to the gills, rather than forming gas bubbles in tissues. Oxygen oversaturation can cause its own problems, but the classic cause of gas bubble disease in aquaculture contexts is nitrogen.