Just to add to this. I have a 10 gallon tank that I've been running as a 'QT' tank (well... I haven't used it yet... but it's been set up about 3 months now under my frag tank). It has a couple of pounds of pukani dry rock (rubble) and a pound or two of BRS reef saver dry rock. The pukani rock is completely covered in coralline algae whereas the BRS reef saver dry rock still looks white with no coralline on it at all and is sitting directly ON TOP of the covered pukani rock. I have heard various reports of the Pukani rock leaching PO4, however, I have not tested my PO4 levels in this partcular QT.
FWIW, my DT was set up with 95% dry BRS reef saver rock and it took it a good year to get a good covering of coralline as well and for my SPS to start growing.
FWIW, my DT was set up with 95% dry BRS reef saver rock and it took it a good year to get a good covering of coralline as well and for my SPS to start growing.