It takes a good 6 months for the rock to be covered in coraline. It will happen but takes a while to get started. Typically, green algae, diatoms, brown algae and cynaobacteria will run their course before the coraline. Coraline algae needs good levels of Mag, Alk and Ca as well. Get rid of the texas holey rock and replace it with reef rock. It isn't any good. Sorry. Typically the lighter the rock the better. You can usually find good live rock on this site for a couple bucks a pound.