Hi. We have had our 25x45 43,000 gallon gunnite inground pool now for over 10 years. It is still chlorine based with a Polaris 380 and slide.
We had a terrible time with alge the first three or four years. We also had sharp calcium, flesh scratching, bumps on the sides and bottom.
We now have a beautiful pool...always.
1. We use straight 8.25% concentrated liquid chlorine bleach...no additives!
2. We backwash the filter for a full 3 minutes. Two times longer than it takes for the sight glass to show clear.
3. We use only 60%, polyquat..., algecide.
4. Brush, brush, brush...there is no substitute for brushing the sides and bottom of the pool at least once a week.
5. NEVER add algecide or bleach during the day. Wait until the sun goes down. Add algecide, wait 45 minutes, add bleach.