Thank you all. Much appreciated. I have been away from home for about week now. The pool started turning green about 3 days ago. I have the test results before I left home and will do the tests tomorrow and post both results.
FC has never been a problem. I maintain a log of all tests on a weekly basis and chemicals added. Last few months:
FC: always >3
CC: 0
PH: between 7.2 - 7.6 (depending on rain)
TA: 70 - 80
CYA: 75-85
CH: 250
Temp - 75-79 deg. (up to 90 during summer months)
Typically, over past few years, I have used on average about 1 gal. liquid chlorine from Pinch a Penny per week. Pool is exposed to full sun and chlorine consumption in summer is little higher. I have always been very particular about maintaining the water chemistry / balance. Always erred on little higher chlorine than lower due to our tropical climate. Pool is open throughout the year.
I live in Miami area by a small tidal river mouth - "Brackish water" (about 100 yards from bay). River is chemically clean but has lot of algae and fish big and small. Pool has no leaks, no stains, vac/pump operates about 10 hrs / day. Pool gets scrubed regularly. Typically, My travel is unpredictable and can last between few days to max about 3-4 weeks at a time. Normally, the pool is crystal clear blue most of the time but sometime, it starts turning green overnight. (Typically I have noted day or two after the lawn is mowed, but there has never been any grass clippings in the pool). My wife helps in testing and adding chemicals during my absence but not as methodolically as i do.
I have conducted various test for overnight chlorine loss etc. Follow the shocking process / cleaning and pool clears up very quickly after shocking it with liquid chlorine. (in 24-48 hours).
I dont have any issues with shocking the pool to get rid of algae 3-4 times a year (in tropical climate). I have never used any algaecides. Pool is not used a lot but I like to keep it in very clean condition. What I am looking for is a little helping hand from ionizer or mineral additive if it really works as some people say. Nature 2 claims that it will not stain the pools. I am not sure about effectiveness of solar powered ionizers or stability of in-line ionizers. I know there are no magic solutions but I am willing to experiment / try.
Thanks for your help.