I'd like to post this after seeing and hearing about some major die-offs in recent history.
I've come to realize that the #1 killer of fish and inverts is peoples' extraordinary inability to do things slowly and patiently.
If an aquarium is set up correctly and cycled in the normal amount of time (4-8 weeks) and stocked appropriately, it's pretty hard to kill the inhabitants.
No magic potions or devices need to be used to achieve this, just time.
Money certainly can help but is usually used to speed things up to their demise.
90% of the fish out on the open market are pretty hardy and easy to keep in captivity.
Virtually all of the aquacultured inverts are getting more and more indestructable with every generation grown/fragged in captivity.
With the sheer amount of cloned products that are as good or even better than the originals, it's easy to have far more superior equipment than we had in the 90's for half the cost.
Even with all these benefits, people still kill fish and inverts in record numbers. If this were dogs and cats, people would be in jail.