As far as calcium tests I say salifert is good. It is a bit a long testing process but accurate none the less.
Just add my experience with my mandarin. Tank is 5 years old. I tried one 3 years ago with no refugium and no sump. He never ate frozen and destroyed my pod population in 3 months. Only lived for 5 months. My current setup has refugium and sump and ton of pods
. I have had my new Mandy for just about a year now. He is fat eats frozen and still takes pot shots at pods
all day long. I feel lucky and hope he continues to eat frozen. I have even seen him peck at flakes.