Why Are My Fish Gasping at the Surface?

Fish at the surface are trying to get more oxygen or escape irritants in the water. Check ammonia and nitrite first — both can cause rapid breathing at any level above zero. A partial water change and stop feeding are immediate steps.

Low oxygen happens in warm, overstocked tanks with poor surface agitation. Increase flow or adjust the filter output to ripple the surface. Overcast days and crowded tanks worsen the problem.

Heat spikes from a stuck heater also raise metabolism and lower oxygen carrying capacity. Verify temperature with a second thermometer. Log the event in ReefDiary with test results so you know which cause fit your tank.