It does seem like a lot of life span data is just best guesses, under optimum conditions. I too have those occasional ancient fish that don't listen to that stuff either. I think sometimes you just have the best water and husbandry for certain species. I have the same thing with house plants...
Despite what I read and others say, many of my bettas don't live long, 6 months to 2 years for that occasional one. They have been bred so intensely and are probably terribly inbred. The fancier the variety the less hardy they seem. There are still some short tailed and wild type that are a bit...
Those are all some spectacular tanks, yours and the others, I tried plants but didn't have the desire or interest to do it right so it of course didn't work out. Again very nice.
One of my angels got Popeye than died, probably still from the heater failure from a few weeks ago, eventually I'm keeping just goldfish. I did lose the one who had Dropsy, he was older and probably had something internal wrong as he took months to fully fill up than die despite trying to treat him.
When my tank heaters went out a few weeks ago, one of my bettas was doing that afterwards, I assume it was from being chilled, I too used Epsom salts, he did get better but than he died about a week later. Betta are touchy fish sometimes, hope yours get better.
Cleaning up and making sure there's no uneaten flakes will basically starve them out and you will see less and less. I freaked out the first time I saw them in my ten gallon too. They occasionally could eat fish eggs but do nothing to the fish themselves. I found satisfaction in sucking them up...
Don't feed as much, clean the gravel, and salt can help, it may take a bit to get them under control. Bettas often don't clean up their food. You could add some Cory cats to help with cleanup.
Keeping your gravel clean will keep them under control, they won't harm the fish, the extra waste will so hopefully you have a gravel siphon. The fish can even eat them.
I can't recall the name of them, they are harmless to your fish, but they are there to feed on the debris in your tank, you need to siphon your gravel out, there's too much uneaten food. I used to see them a lot when I first started keeping fish, I now do more water changes and bigger ones and...
That's one of the reasons for wanting to keep only goldfish, heaters aren't necessary. I do have them in my fancy goldfish tanks to bring the temperature up to 65, my basement runs around 60, if the heaters fail it isn't a tragedy like it is for tropical. A turtle sounds cute, I would probably...
I still have 9. It's okay, I did plan to swap out my 55 and 75 gallon in the fall, putting the smaller goldfish into the 75, and moving my tropical into the 55. Eventually I may just keep my goldfish, but it could be quite a few years before I lose all my angels, though some are around 5 year...
They were all lost because of the heater failure, the betta developed Dropsy, used the Epsom salts to bring down the swelling, but he died a few weeks later, it obviously damaged him internally, the angels just died, no symptoms.
One of my older larger goldfish has Dropsy, getting to look like a balloon, still eats well though. I haven't tried any treatments because I believe it's a self limiting systemic thing, not sure if it will eventually suffocate. It's been slowly getting bigger since last fall, it's scales are...