As some have already eluded to...the problem with the "add with caution" fish is that they may be fine for long periods of time, varying depending on species and such, and then all of a sudden go crazy. Some say that keeping them well fed may curb this, but from my experience I have noticed that chances of this happen are greater once the fish has been in the tank for a while and reaches maturity, but I am sure there are plenty of examples otherwise. You are correct though, the more extravagant the fish means we cant have it or the harder it is to keep lol. Come to think of it, isn't that the reason why we got into saltwater tanks anyway? Because we were all sick of having dull brown freshwater fish and simple tetras...