A sick aquarium fish usually shows clamped fins, loss of appetite, gasping at the surface, or unusual spots and discoloration within a day or two of the problem starting. Test your water first — most illness traces back to ammonia, nitrite, or temperature swings.
A sick aquarium fish usually shows clamped fins, loss of appetite, gasping at the surface, or unusual spots and discoloration within a day or two of the problem starting. Test your water first — most illness traces back to ammonia, nitrite, or temperature swings.
Behavioral Signs
Hiding constantly, loss of appetite, erratic swimming, or gasping at the water’s surface are all early red flags worth acting on quickly.
Physical Signs
White spots (ich), ragged fins (fin rot), a swollen body with raised scales (dropsy), or cotton-like patches (fungal infection) each point toward a specific, often treatable problem — see our health and wellness guide for details on each.
Water First, Medication Second
A large partial water change is often the single best first response while you diagnose further — many symptoms improve or resolve once ammonia and nitrite are back to zero.
FAQ
Test your water parameters. Ammonia, nitrite, and pH problems cause the majority of symptoms mistaken for disease.
Some diseases, like ich, are contagious between fish in the same tank. Isolating an obviously sick fish in a quarantine tank when possible reduces the spread.
It varies — ich can spread within days, while chronic conditions from poor water quality build up over weeks. Early water changes give you the best chance either way.
