@Graham/Mark: I have read conflicting things about DSB some say you need worms etc others say that the turning over of the DSB introduces too much O2, It did have our native snails that do turn over the sand but the fish keep eating them. There is a 5000 l/p wave maker pointing at the bottom/sand that should help move some water through the DSB
I know that with cold water and a low pH that ammonium/ammonia balance is well in my favour.
"pH appears to be below 6 on the graph, and that would stop the nitrogen cycle" That I didn't know, it is very close to a pH of 6 or below, chart only goes to 6.
@Adrienne: Yes it was in tap water, always done them that way. Maybe it always does a mini cycle after I wash them, just have never tested the tank before