Kenneth Ho wrote:

I keep getting this strange results from all of my GH test kits, which
I assume is due to extremely soft water, but I need confirmation from
you guys. I have FishDoc, Duplam, and Sera GH kits, all instructions
said that as soon as the test liquid turns green then it's done. Okay,
first drop, the colour is too light, I couldn't tell anything so I
continue to second drop, orange, third, orange... etc. I have tried 30
drops, and I still couldn't get it to turn green.

Is it possible that it actually turned green in the first drop, but
the concentration is so low that as soon as I put the second drop into
the tube the colour would turned back to orange? I am very sure that
the water isn't hard since my tonina is thriving.

Since you get the same results with all three kits, believe it. Your water
is too soft to measure. Same thing happens when you test RO water.