Why do fish die so quickly?
This may be a philosophical question.
My 20g tank is well established, and my water parameters are fine - nearly 0 for ammonia and nitrite, pH is 7.4 which is fine for goldfish. Plenty of filtration and I keep it pretty clean. Temperature in the upper 60s, fine for goldfish. The tank is not overpopulated - no more than 5" of goldfish. I feed them a pinch of flakes once a day, and supplement with fairy moss from my outdoor pond, and dried seaweed, for roughage. Sunday is fasting day. There's dried tubifex and frozen bloodworms for treats.
So I buy fancy goldfish from the big box stores (but not Wallyworld) as that's all there is here. I watch them carefully before choosing, then bring a healthy one home. It won't eat much once here, gets lethargic, stops eating entirely, sinks to the bottom of the tank, and dies over the course of a couple or three weeks. I'm talking 2" goldfish that have obviously been kept alive and eating for a year or so wherever they came from. Fancy ones, orandas and such. Not feeder fish.
I was told by someone who used to work these places that they refrigerate the fish to ship them, and sometimes they get a bit too cold and never really recover. But why would they go from the picture of health at the store, to dying as soon as I get them home? I float the bag in the water to acclimate the temperature and then add some tank water to the bag to acclimate the fish to the water chemistry before letting it out. Are they going into shock from the water change? Is this just how it is with buying fish, always a gamble? I'm tired of taking home a gorgeous calico fantail or whatever and feeling like I killed it.
Plus, even those that don't die right away, don't live much more than a year, and I thought goldfish are supposed to live for many many years.
What's the scoop on goldfish longevity?