Fish Die After Heavy Rain: Spring-Fed Pond Mystery

Recurring Post-Rain Fish Kills

Spring-fed, bog-bottom pond. All fish die after heavy rain—happened before.

Rain-Induced Stressors

• pH crash: Rain is acidic (pH 5–6), no hardness. Dilutes pond buffers.
• Oxygen drop: Rainwater low in O₂; runoff adds organics that consume O₂.
• Toxic runoff: Pesticides, herbicides, gasoline, fertilizers from surroundings.
• Temperature shock: Cold rain into warm pond.
• Gas supersaturation: Rain splashing can trap nitrogen.

Investigation Steps

1. Test pH, KH, GH, ammonia, nitrite, O₂ *during/after rain*.
2. Identify runoff sources: lawn, driveway, agriculture, roads.
3. Divert runoff with berms or swales.
4. Add aeration (air stone) to buffer O₂ drops.
5. Maintain KH > 100 ppm with crushed coral or buffer.

Rain changes chemistry fast. Data during events reveals the killer.