Del-
Sometimes fishkeeping, like any other hobby, is backed by a little bit of luck. You never know if your fish will get along or not. You never know if your fish will feel comfotable in your water parameters. Some people have a wild mixure of fish that all get along, some people have 2 fish that are in a death match.
Sometimes you put a fish in perfect water and it dies
what if its the fish or the way its taken care of and not the water itself?
sometimes you put a fish in average water and it lives.
what if nothing is wrong with the fish?
You never know with each fish having a different DNA makeup and coming from a different source.
but do we know that DNA has anything to do with it? and what would bew these different sources? afew example please
I have a community tank with neons, CL's, plecos, and non-agressive cats(.5" striped rapheal, synodontis, banjo cat) and have had no damage to anyone for months. I added a 1.5" royal pleco 2 days ago, and 12 hours later saw a CL eat out its eyes. Both fish seem to be doing fine, but the royal doesn't move as much anymore.
Probablitity/chance?
It is almost all based on luck when you are dealing with things that have brains, because each one is going to be different, so you never know what you are dealing with...