I think in the wilderness there is enough acro to spread the harassment around so that no acro suffers severely.. however in a small hobbyiest environment there just isn't enough acro to go around.. they also tend to pick a favorite dont' they? always your nicest ones. .i guess pretty acros taste the sweetest
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Well i don't think the books like to mention that the gobies are 1 inch of acropora munching evilness.. bad to stock these sorts of books in stores selling Clown gobies.
Could be that the polyps didn't extend because it was feeling stressed from being burned.. If you take a flourscent light acro and introduce it to bright MH it does undergo alot of stress.. despite it probably wanting the bright light... maybe that's what happened with you?