Persistent Nitrite After Pond Repair: Tap Water Source

After crack repair, refilled pond; nitrite stuck at 0.5 ppm (1+ week). Ammonia zero. Tap water tests ~1 ppm nitrite. Also brown algae (diatoms) in sunny pond.

Tap Water Nitrite

If tap has nitrite, biofilter must process it. Verify with second test kit. Add beneficial bacteria + pond salt (reduces nitrite toxicity). Carbon filtration may remove some nitrite.

Brown Algae (Diatoms)

Diatoms = brown film, wipe off easily. Like low light; unlikely to persist in sunny outdoor pond. Snails/algae eaters may help. See algae guide.