Thats right, thats a 2.0 on the little card that comes with the kit. I guess this will start to go a darker purple once the ammonia reading comes down to a yellow colour on the card, 0ppm.
Do I need to get some ammonia do you think to help the process along? I guess there must have been some ammonia lurking somewhere, the only place I can think is like you said, from the gravel, but I did ensure it was running clear water when I rinsed it. Curious, said alice?!!!