My Salifert kit says NSW is 400-425.

I've always wondered why people are below this level and unconcerned, whereas they are always wanting higher than normal Alk levels. :confused:

I've never been below 410 using Kent salt.

Agreed Deb, it never makes sense to only look at only one of Ca or Alk; you HAVE to look at both numbers to make any sense of things.