Thanks to your help and some great persistence and a diverse range of chemicals, my pool is now much healthier...
And that's my problem. The test procedures state, mix 7ml pool water and 7ml cya reagent for 30 seconds, then drop by drop into 9mL tube until you can't see the dot. Trouble is, If I go fairly quickly, say 2 drops per second, my finish is at 100. If I let it settle - for even seconds - I can add a LOT more. My assumption is that there's little oxygen bubbles in there that are popping.
So that's my question, is there a wait period between drops to let it settle or do you read it quickly?
To put it simple,if the results are accurate after settling a minute or so, my pool has very little CYA in it which would explain partially why all of the bleach I put in would get depleted VERY quickly. It would also explain why at a perceived CYA of 100, temp of 65 and 4 3" tabs in a floater is keeping my pool crystal clear and aglae free despite being set on the lowest setting and only producing a .5 FC reading.