If you can get a EC meter, yes it would be better to have that, but if they have already sent it out, its not that big of a deal.

I am not super familar with sodium and don't want to give you incorrect advise, from what I remember it is bad for your plants. I am not sure at what levels it becomes a problem though.

Might want to do a little research on the subject, if you find some interesting articles, post them up here too.:thumbsup: