Possible cause
Stress or Early Illness
In an established tank, prolonged hiding or loss of appetite is usually stress or the early stage of an illness that hasn't shown visible symptoms yet. Test your water first to rule out a quality issue, and keep a close eye out for any visible symptoms developing.
Why this happens
- A water quality issue that hasn't shown up as a visible symptom yet.
- Recent changes — a new tankmate, rearranged decor, or a move to a new tank — can cause temporary stress.
- The early stage of an illness, before external symptoms like spots or fin damage appear.
What to do next
- Test your water first — ammonia, nitrite, nitrate, pH, and temperature.
- Watch closely for any developing symptoms (spots, discoloration, clamped fins) over the next few days.
- Reduce other stressors: check tankmate compatibility, avoid unnecessary decor changes, and keep feeding consistent.
- Consider a quarantine tank if you suspect illness, to observe without risking the rest of the tank.
Frequently asked questions
Why is my fish hiding and not eating?
This is usually the earliest sign of stress or illness, before other symptoms appear — testing your water is the first step since a hidden water quality issue is the most common cause.