personally, I find there are quite a lot of fish kept that long by seasoned peeps(longest fish I had is a cory for four years), however not these toothy preds.
I'm all about committing to keeping fish long term too, but 20 years is a ridiculous length of time to keep a fish. If I keep Max for 20 years- and I certainly plan to try- my son who was born in January will be a sophomore in college once this time period is over. Think about it like that. I have the best of intentions, but I honestly don't know if I'll be able to make it happen.
