Honestly I think it has something to do with the city water of each state or city. We know magnesium will help grow coralline along with stable parameters. My tank has been super stable but it will only grow on my rocks, power-heads, and in the overflow teeth. Recently my frag rack exploded. I’ve never had it grow on the back glass. Ever. I used to think it was from running too clean, but this tank has seen very heavy nutrients and Nutrition with higher Mag and Cal, but still no growth on the back glass. It’s one of those things that will forever haunt me.