This is a total myth in the hobby that keeps getting parroted.
I should have made clear that it was a generalization (more so than a myth) because you're right, it's not a rule. My current tank had SPS in it around month 3 or 4. But I think it's nonetheless a safe generalization for people just getting into keeping SPS considering more likely than not, a new reef will have multiple swings prior to 6 months or even within the first year. But you're correct, it's not a hard-fast rule. I do, however, believe that my following statement in that same post, is a good rule of thumb (that once corraline is taking hold on the rockwork, the tank is suitable to begin SPS).
Was just trying to give conservative advice to help prevent a fellow reefer from spending a bunch of money on expensive coral only to potentially lose them a month or two later due to an immature reef, but should have been more clear and let them make the decision with the given knowledge.


