we have been using a pool service since last fall because the pool maintenance manager (ie me) started traveling a lot for work. Well with all of my new found time at home I decided to check in on the chemicals because I discovered that my pool guy doesn't even brush the pool when he is here. I watched him dump in a gallon of chlorine, turn on the pump and leave 3 weeks in a row. I noticed the front of the spillover had hard build-up on it that my dad thinks is efflorescence but was REALLY hard to get off, and the beginning of some yellow algae in a few corners of the spa. So I broke out my trusty pool map app and found calcium was at 200, Ph 8.0 TA 110, CYA 20 FC 1.0 and CC 0 the morning after he had been here. I was adding 1 gal liquid chlorine myself 2X week at night but not doing any water tests. (I know -shame on me!) I followed app directions and added calcium, stabilizer, and acid and am now sitting at Ph7.5, TA120, CH 375, CYA 30 and CSI is 0.14 and am keeping the FC 3-4 consistently. Since it seems the algae is dealt with now I added some Algaecide 60 Plus from In the Swim. Pool water is crystal clear. FWIW, Lime Away and a 6" putty knife did the trick. Just curious if this nastiness was related to the high Ph/Low calcium?