usually one year is a basic guideline, but if you are looking to house a certain animal, the word 'established' can vary depending on that animals needs.
As for the coralline, if you are lacking calcium in your system, it doesnt matter if youve had the tank for a year or so... it needs calcium.
Try dripping kalk or something.
My tank was started 1/07 and it has tons of critters and coralline. The coralline spreads like a weed. I consider my tank somewhat established just because of the biological balance and growth, not necessarily just time.