Green water (algae)
- Set the pH to ~7.2.
- Do a strong shock chlorination.
- Brush walls and floor.
- Filter for 24 h straight.
- When the water turns from green to milky-white, add flocculant or use the filter, and vacuum the bottom.
- Restore the chlorine to a normal level.
Cloudy or milky water
Usually high pH/alkalinity, poor filtration or excess product.
- Check and correct pH and alkalinity.
- Filter more hours and check/clean the filter.
- A flocculant helps clump the particles so the filter can catch them.
Stains or slippery walls
A slippery wall means algae are starting: brush and chlorinate before it gets worse.
Prevention
Stable chlorine, in-range pH and enough filtration prevent 90% of these problems.