Is it always necessary to glue or putty the frag plug to the rock in the the tank? My Caribe Sea rocks seem to have a lot of nice pre drilled slot holes in varying places and the stem of the frag plug fits perfectly in the hole. If the Coral is level and does not appear to be in danger of blowing out due to water flow, is it necessary to still glue it in place? I was thinking that it would be easier to move if needed and less unnatural substances being included into the water column of the tank. Will coraline algae eventually adhere the plug to the rock anyways at some point?