Foam and High pH After Mortar Waterfall: Water Changes and Carbon

Mortar Effects

Mortar leaches calcium hydroxide → high pH (8.5–9+) and hardness. Foam is from dissolved organics/proteins, not phosphorus. Lava rock does not remove foam.

Fixes

1. Daily 10–20% water changes until pH stabilizes 7.5–8.2.
2. Activated carbon in filter (replace monthly).
3. Acid wash waterfall (vinegar scrub) if accessible.
4. Test pH, KH, GH daily.

Phosphorus Note

High phosphorus alone rarely harms koi; it fuels algae. The real danger is pH >9 converting ammonia to toxic NH₃.