Hi , thanks for re-asking about this . I think your right , that is why I posted the picture because it took so little of water it never registered . Confused me that one . The early test strips test , never even changed the colour of the paper , so again confused .Are you sure about this? The picture you posted shows the level really low in the tube. That would indicate really high CYA, not 0. Can you check this again or post a better picture?
Here are couple pics
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