When coral cover the lid completely or achieve a growth of 1" around in any direction i remove the lid from the tube, together with coral, and glue them on disk, always removing the air between the lid and the disc with the glue. May be used two components epoxy to glue, heat melted glue used by electricians to fix electrical cables to the wall, Thorite, etc.. If eventually coral base has covered the lid and propagated to the tube, i cut the tube immediately below the coral extension, fill the conjunct with glue to remove the air and fix the piece on the disc.