I am one who says save your money on these additives and just keep your water quality high and CA
levels between 400-450. I have never dosed anything other than CA
in my tank and you can see the coralline in my gallery if you like.
I read somewhere here that coraline algae likes less light.
I have intense light in my tank and coralline grows everywhere. Even the loc-line nozzles that are in 2-3" of water directly under a MH
light. I also have coralline growing in my sump with less than 1 WPG
of light. I have talked with Mike at liverocks.com and he stated that coralline it more plentiful on the side of the rock that does not get as much sunlight. I am going with "it is true" in nature with real sunlight but in our tanks where it is next to impossible to get the intensity of the sun it is not a factor to be concerned with.