How to judge health of SPS corals
 

how do I tell how my acropora are doing? polyp extension? colour? both? haven't had mine for long but they're all showing a lot of polyp extension. one piece is showing a small bit of bleaching near the center of the coral. how long does a full-blown bleaching event take?

Depending on the type of coral, they can become totally bleached within a week. My personal experience is that acros are much less suseptible to bleaching than are encrusting montiporas. Try moving the coral to lower levels in the tank or move to an area with greater but still dispersed flow. Hope this helps.

Polyp extension and colour are both excellent signs that sps are doing well in your tank.