how do I get more good algae

[fishguyxd]

Well my water is currently low in ca and alk so I have seen some posts saying add this and that I have been looking at some reef builder solutions seachem/kent ca/alk increaser. How well do they work (time frame)and how much do I add. I am trying to get more coraline algae in a 6+ month old 72 gal tank I have none (purple type algea) on glass and only some on the LR that it came with, but it has not progressed I only have a little bit of brownish type algea. I just don't want to buy these produsts and find there no good.any comments or ideas. please and thanks[/b]