Disagree on the stars. While managable, they can definitely destroy nice zoa colonies if left unchecked.Bristle worms, and asternia stars aren’t even pests. The trick for monti nudis is super glue the underside around anywhere you see eggs/ bites after scraping off what you can. Aefw are annoying and if you don’t keep a close eye will kill things but once aware you can keep a tank healthy and thriving with regular blasting of corals/wrasses that eat them, or dips if your corals are easily removed. They also tend to have favorite acros which can act as a canary.
hmm so with that said if You take unchecked aefw off the table, I’m going with vermetid snails... but even those tend flair and the sorta exhaust whatever they consume and die back..
Not too hard to deal with.Monti eating Nudi's.
I will never put a monti in another sps dominant tank again.
I have 7 montis in my 120.
3 are large colonies.
I had monti's about a year ago and nothing since.
I outbreaks on 2 different monti's that I can see.
My tank is too grown in to take anything out.
My working upgrade will be 95% sps zero monti's, as much as I like them.
Aiptasia are barely a problem nowadays, you only ever hear about people putting in work or predators to get rid of them, never really about people restarting their tank or giving up entirely because of them anymore.
All the things you listed just vary in how annoying it is to deal with them, but you can deal with them, so they hardly qualify as the worst.
I'd say a good contender are fish attacking blood sucking isopods, nothing you can really do besides going fallow for a year or more, trying to catch them every night basically forever, or restarting the tank
Maybe coral diseases leading to stunted growth forever
Because you tried everything and nothing worked and you had a real problem with them killing your corals, or as a convenient excuse for the upgrade? Im in quite a few local whatsapp groups and you are the first time i hear about someone doing this pretty much since i started a couple years ago, only ever as horror stories of the past and in old booksI'm restarting/upgrading right now because of them. Trying to find a way to keep my LPS without bringing aphasia to the new tank with them.