Cesspool-Smelling Large Pond: No Outlet = Stagnation Death

30×100 ft pond, 2–12 ft deep, brook-fed, no outlet, 200 goldfish + 1 koi, smells like cesspool. No outlet = no life. Stagnant decay = hydrogen sulfide.

Why It Stinks

• Inflow = outflow required. No outlet = accumulation.
• Fish waste, dead leaves, dead fish → anaerobic bottom → H₂S (rotten egg).
• Pump circulates but doesn't export waste.

Fix: Create Outflow

1. Skimmer-style outlet: Buried PVC from far side to creek — gravity flow.
2. Equal in/out: Same volume in = same out.
3. Flow = life: Prevents stratification, exports nutrients.

Cleanup & Biology

• Drain low, vacuum sludge.
• Add large common carp — bottom vacuum cleaner.
• Plants, plants, plants — marginals, lilies, submerged.
• Run pump 24/7.

Proof It Works

Author has similar pond + outlet + carp = clear, healthy, 20 koi, 200 goldfish, frogs, snakes, newts.

No outlet = septic tank. Build the drain. The pond will breathe.