So it all started when my finacee said "I wouldn't mind getting a little fish tank with a goldfish", but I don't want to spend more than about £20-30 (uk pounds) on it. (haha!)
Looking on ebay we thought BiOrbs were the way to go and thought about getting one second hand, but then went along to Pets at Home and saw a 25 litre (6 gallon (I know, I know!)) tank one sale for a small fortune but we got that and they said to put some water in with conditioner, let things run for a week, come back and get your fish.
So we have the tank running for a week, come back and get the fish, a fancy goldfish, mostly white with a red stripe down its back. Swimming around all happy. After day 3 we wonder what the white spots are on it's tail, day later we notice it's got some sort of bug hanging onto it's tail (argulus as it turns out), day 5, dead fish
So we scrubbed everything down, bought some new gravel, set everything up for a week again, went and got a new fish, straight tail this time. Fine for a week, then did a 15% water change and within a day of that he had white spots, it was 2 days later before I'd found out it was Ich, put the treatment in the next day but the day after he was dead
So, started again... more scrubbing and new gravel. But the water treated with machalite green instead this time. A new fancy bright gold fish, spent a lot of time hiding in corners and refusing to come out except for food. Water tests at the store said there was nothing wrong. Week 5 he developed a swim bladder infection and died within 2 days
As you can imagine I was rather miffed with that tank and didn't want to get another fish in it just to watch it die, and by then I'd of course realised 25 litres is far too small for a goldfish.
So went out and bought a new 64 litre (17 gallon) tank, and have 5 black widow tetras in there, which seem to be ok apart from being scared of the light.
So from just wanting a little goldfish in a little tank we now have a big tank (not big by some standards but it dominiates our house!) and have spent several hundred pounds!