Daily Goldfish Deaths in 5-Year Pond: New Fish or Water Change?

35 Goldfish, 1–2 Dead Daily After Changes

Established 5-year pond. Recent: 2 new fish (unknown), large tap water addition with conditioner. Fish gasp, separate, die. No visible disease.

Suspects

1. New fish introduced pathogens (parasites, bacteria, virus). No quarantine.
2. Large water change shifted chemistry (pH, GH, KH) despite conditioner.
3. Low oxygen: Hot weather? Waterfall may not suffice. Test O₂.
4. Gill flukes/bacteria from new fish → gasping, death.

Actions

• Test full parameters (pH, GH, KH, ammonia, nitrite, nitrate, O₂).
• Add aeration (air stone) immediately.
• Salt (0.1%) + MelaFix for supportive care.
• Quarantine new fish if still separate.
• Contact local pond club for microscope diagnosis.

5-year-old goldfish are NOT old (can live 20+ years). Find the trigger.