They dont seem to be deadly, ive heard that they slow down the growth...see my burnt red Acro doesnt have these guys but my blue tipped Acro does? both of my acros are frags and actually i had to break off a piece the other day due to some bleaching..(it fell on my bubble coral and sat there all day..needless to say it was stung heavily in that are causing it to die off)...my blue tip has growth and my burnt red is fairly new so im not too sure on what the true effects are to these red acro bugs...