Slight green color first day whenever I do weekly add of fill water

[jmbuys]

Water chemistry is good and has been very stable:
FC 8
CC 0
pH 7.6
TA 80
CYA 70

the water is clear and blue, but every time I add a few inches of fill water (1x a week) the water turns a slight green color....lasts about 12 hours then back to blue for the week. Trying to figure out what is in my fill water. I have a well w/ oxidizing/aeration filter to remove Iron and manganese. I've tested the fill water from well (after filtration) w/ strips and as part of yearly well check just sent it to lab for analysis, water after filter came back w/ 0 iron, 0 manganese and 0 copper....so can't figure what else is in fill water (mineral etc) that can cause the temporary color change. Any ideas appreciated.

 

[Spa Owner]

First guess would be iron. It reacts with chlorine to create a green colour for a day or so. However the lab returned 0. Is that ferrous or ferric iron at 0? Could it just be the well water is green after treatment and the chlorine needs time to work? The 12 hours is simply turnover and chemical reaction time.

 

[jmbuys]

Testing didn't indicate Iron type tested, but the purpose the the aeration filter is to take it out of solution w/ higher pH and w/ oxygenation so it can be filtered out, so after filter there should be neither ferrous or ferric I would think. Luckily the water before or after filtering isn't green! , as we drink it too. I would think Iron too but not seeing it...might have thought copper or maganese as other potentials but not there...wondering if it could be another metal? Might stick some poly-fill in the basket see if it's picking up some kind of metal.

 

[Spa Owner]

Not wanting to belabour the point, the water may appear clear in small amounts even a bath may not look off colour but the actual colour shows up ina larger water body like the pool perhaps.

 

[jmbuys]

anything is possible but my wife would freak out if she noticed any Hint of green color in our white bathtub ...even if that was the case same question what mineral in plain water causes it to be green...at least in pool iron w/ chlorine produces the green...but in water from a well that tests clean. only things i know outside algae for pool is iron and copper...guessing there is no other reaction that can cause green

 

[Spa Owner]

guessing there is no other reaction that can cause green

Sure would be I am certain. But how many times would it be come across? If chlorine clears it the assumption would be it is organics of some sort likely algae, but could be something else. Organic chemistry is too hard to work out to know for sure.

I forgot to mention...blue pool slight green water water colour could be yellow/brown. Yellow brown is tannin and that sort of product and not something we would test or. It would consume chlorine and bleach out.​