Hello catba,
I just found this topic-Welcome introduce yourself-, saw you had no replies and felt I should not let that stand. So, I guess you could call this a "pity post" but you shouldn't.
I've been keeping fish about seven years. not that seriously. just like them. My enthuziasm waxes and wanes.
I hope the posts you refer to have informed you about keeping tropical and cold water fish seperately. You know goldfish are cold water guys. That means they metabolize their food differently so they make more waste and require different types of food.
I know how you feel about having a fish for awhile. I would be the last to suggest that you get rid of your fantail. You could keep it in a nice bowl and even get 'em a tankmate. I've seen goldfish live for years in a real simple setup. Feed them very little- like one flake a day- or two or three flakes every other day. Change about half the H2O every week. (seasoned water, one week old, at room temp) If you want, run an airstone in the bowl.
Make sure if you do this, get the biggest bowl you can and get one with a wide opening. Water surface is key for oxygen exchange. If you get one with a narrow opening fill it 1/2 way to allow for oxygen
Anyway, Nice to meet you and good luck.
My name is Paul. I live in Philadelphia USA.
Goodluck and See you on the board.