Rule #1-Make sure your fish don't fit in each others mouths. Lol! It's the only way I lose fish for years now, predation.
Seriously though to me fish care is pretty straight forward.
Rule #1 is information. Always research a fish before purchase get to know it's habits, aggression level is it a predator....etc.
Rule #2 source a quality vendor. This can only be done through trial and error, but once you know where to go stick with them.
It builds a relationship and they're much more likely to look out for you if your a known loyal customer.
Rule #3 water quality. Don't ever skimp on water changes and monitoring your water quality.
Rule #4 Quarantine. Always quarantine your new arrivals, even from a good vendor there's always a chance you may get a sick or
overly aggressive specimen.
Rule #5 Always have a holding tank in case there's a community breakdown. Sometimes the death of fish leads to anarchy in the
fish reestablishing a pecking order.
Rule #6 Always make sure there's plenty of cover for fish incase your not home when anarchy breaks out. If I can't find fish the
same size I size my decor accordingly. Make sure there's a decor piece that the smaller fish can retreat to, but that the bigger
fish can't follow.
Rule #7 always seek out help hear when it comes to quality filters. These people are in the know as they've had real experience
with the equipment and usually long term. Price is definitely not always a sign of quality when buying filters.
And that's about it as far as the rules I've followed. It's working for me so far, I've got an Armatus that's over 2 years old and has
survived breaking my glass tops with no ill effect, had his dorsal bitten totally off by my Curupira and it grew back in a month and he's
still kicking. While many have had them die suddenly or killed themselves running into glass walls. Don't know if I'm lucky or if I'm doing
something right. I prefer to think the latter.