WATER PROBLEMS
pH swings (night vs morning)
If fish flash and water tests “look fine,” pH instability is a common hidden cause. The fix is usually KH/alkalinity—done safely and gradually.
What a pH swing means
Many ponds read one pH in the morning and a different pH at night. Fish tolerate a wide range, but they do poorly with rapid swings.
How to confirm
- Test pH late evening (after a full day of sunlight).
- Test pH again early morning (before strong sunlight).
- If the difference is noticeable, test KH/alkalinity.
Most common cause: low KH
- KH is the buffer that prevents pH from moving.
- Low KH = pH can drift or crash, especially overnight.
- Low KH often shows up as flashing, irritability, and poor healing.
What to do (safe sequence)
- Confirm ammonia and nitrite are 0 (fix those first if not).
- Raise KH gradually (spread adjustments over days).
- Re-test pH (night + morning) and KH until stable.
When it’s not KH
- Over-aeration microbubble irritation or gas supersaturation
- CO₂ retention (especially in covered ponds or low turnover areas)
- Recent big cleaning or filter disturbance