shrinking corals!

[Duncan Frags?]

My friend tells me that some corals shrink and die. Others say this is a lack of something. What does everyone here think of that?

 

[Hormigaquatica]

Shrinking coral is rarely a good thing, but it doesnt necessarily mean they are about to outright die.

First thing to do is check your water parameters; make sure you havent had a spike in nutrients (Nitrate or Phosphate), or a swing in KH and/or pH. Also check your salinity, and make sure the temperature isnt swinging too up and down.

Others say this is a lack of something.

I will say, coral rarely suddenly shrinks up because of a gradual reduction in something. A sudden reaction is generally brought on by a sudden change.