and pests.
is coral color a necessary requisite for health? doesn't color appear as a result of less zooanthella which shares a symbiotic relationship with the coral?
+1.
Plus polyps extension on SPS and how big and full the polyps on LPS are.
Also it's ability to survive a less than perfect environment like a small phosphate spike, overdosing something etc. a healthy coral should pull through with no major issues.