I dunno if you knew about this already, but you can just put fish traps on a stone pool, and it will catch goldfish 100%. Place 8-10 per pools and you will no longer have any issues with getting goldfishes.
Moral issues aside, life gem is incredibly easy to get. Just rape / have sex with any native equipping the fertility item, then feed them the abortion potion. Doesn't even need to wait for their belly to swell.
And I don't know if this a bug or just a translation / message feed error, but despite the text saying the "mother_name died during birth", they will always survive the procedure, so you can just impregnate them again and feed them the abortion potion over and over.
(played on ver 0.12)
Tested on a new save and this seems to be the case. Can't get them to spawn from raids when I haven't "transformed" any elderly with the potion into one of them.
I tried banishing & kill my elder brother / sister, yet the elder brother / sister NPCs still spawns during the halloween raids, so I assume there's like a "trigger" when you transformed one of the grandpa/grandma natives.
Not that it matters though, I don't think there's a player out there who willingly kill / banish their Elder brother/sister NPC after doing all the steps to "spawn" them into their game.