Hi OldMan47, thank you for the warm welcome.
I think perhaps there has been some confusion made on my part. The photo displaying the ammonia readings was in fact showing a reading of close to 0.5 and not the stated 0 in my original post. I changed 50% of the water, twice within the space of 3 - 5 hours to ensure the ammonia had gone. Unfortunately, I misread the results the first time and it wasn't until I did a test 2nd time round and from a sample from the tap that I realised it was in fact yellow (0 ppm) the first time round (made flushing the 50% 2nd time round a waste of time really!).
I have just checked my ammonia levels for today and there appears to be another spike of 0.5 with comparing it with general tap water and the colour chart. I will do another water change soon (25% you reckon?).
Here's a photo showing tap water on the left and tank water on the right. From a first person perspective, the tap water is more yellow than green.