Quick referenceGas bubble disease occurs when supersaturated water releases gas bubbles inside fish tissues + eyes. Caused by leaking pumps drawing air, micro-bubbles, or rapid temperature/pressure changes.
Symptoms
Bulging eye(s) (popeye)
Bubbles visible under skin/fins
Lethargy
Disorientation / spinning
Surface gasping
Hemorrhaging in fins
Cause
Air drawn into water via cracked impeller seals, leaking sumps, micro-bubble overflow, or sudden temperature/pressure drops. Fish absorb supersaturated gas; bubbles form internally as gas comes out of solution.
Treatment options
Find + fix the leak. Inspect all pump seals, fittings, sump returns, overflow boxes. Replace cracked impellers + worn O-rings. Check for cavitating intakes.
Increase surface agitation. Powerheads aimed at surface dissipate excess gas faster. Add airstone for 24-48 hours.
Lower temperature 1-2°F. Cooler water holds more dissolved gas safely; gives fish recovery time.
Salt bath (FW). 1 tsp/gal aquarium salt for 7 days reduces osmotic stress while gas dissipates.
Always treat in a separate quarantine or hospital tank.
Prevention
Inspect pumps every 6 months. Replace impeller seals every 2 years. Avoid undersized return pumps cavitating. Keep sumps from drawing air at intake.
Fatality + outcome
Moderate - mild cases recover in 24-72 hours after fixing source. Severe cases (large embolisms, eye damage) often fatal.