Uh, not to seem like a retard, but how exactly do phosphate and calcium levels affect a tank? And what's KH? I have had my saltwater up and running for about 2 1/2 months now- I test for nitrate, nitrite, ammonia, alkalinity, and pH, but that's the first time I've heard of that stuff. And yes, I've done quite a bit of reading about saltwater (because I was so freakin nervous about the stuff) before I set up my nano reef. Are those tests critical like the other ones?