"The uglies" is not what kills fish and corals. The algae and cyano is part of the natural reef.
What kills corals is the same thing that causes the ugliest - namely, an unstable tank where your nutrient cycle has not matured to a point where biodiversity can keep everything in check and maintain stability.
In young tanks, this biodiversity is generally lacking so generally its less likely to be stable and more risk of coral dying. This doesn't mean all corals in young tanks will die, and there are other artificial methods of mitigating instability and reduce your chances of failure.
This si why some say wait a few months bc in young tanks, esp ones that use dry rock and has sand, it takes a few months for nutrient to even fully saturate the substrate so any "test reading" you get in the first 3 - 5 months isn't really giving you the full picture of what yiur tank is really doing bc a lot of what you are testing for isn't in the water but instead is absorbed in the substrate. This is why people often get to a situation where they think everything is fine, then 5 to 8 months later they suddenly get a bad case of round 2 uglies and corals dying and they didn't change anything in their routine. This happens when yiur new rocks and substrate finally reached saturation and all the "false sense of everything going well"in the first few moths rear its ugly head. This is where the anecdotal "wait eight months" comes from. There is some truth in that just based on all the "help my tank is doing fine the suddenly everything crashed and I have algae everywhere" posts that we have seen over the years.
Patients is key. If you really understand the biochemistry and what the various nutrient interaction that occurs in your tank, then there are ways to make successful tank and add corals on day one. But generally speaking new reefers do not understand that so impatience and adding corals too soon leads to more failures than success.
What kills corals is the same thing that causes the ugliest - namely, an unstable tank where your nutrient cycle has not matured to a point where biodiversity can keep everything in check and maintain stability.
In young tanks, this biodiversity is generally lacking so generally its less likely to be stable and more risk of coral dying. This doesn't mean all corals in young tanks will die, and there are other artificial methods of mitigating instability and reduce your chances of failure.
This si why some say wait a few months bc in young tanks, esp ones that use dry rock and has sand, it takes a few months for nutrient to even fully saturate the substrate so any "test reading" you get in the first 3 - 5 months isn't really giving you the full picture of what yiur tank is really doing bc a lot of what you are testing for isn't in the water but instead is absorbed in the substrate. This is why people often get to a situation where they think everything is fine, then 5 to 8 months later they suddenly get a bad case of round 2 uglies and corals dying and they didn't change anything in their routine. This happens when yiur new rocks and substrate finally reached saturation and all the "false sense of everything going well"in the first few moths rear its ugly head. This is where the anecdotal "wait eight months" comes from. There is some truth in that just based on all the "help my tank is doing fine the suddenly everything crashed and I have algae everywhere" posts that we have seen over the years.
Patients is key. If you really understand the biochemistry and what the various nutrient interaction that occurs in your tank, then there are ways to make successful tank and add corals on day one. But generally speaking new reefers do not understand that so impatience and adding corals too soon leads to more failures than success.