There seems to be the notion around that goldfish mustn't be kept with
tropical fish due to differences in temperature requirements.

IME, it wasn't the temperature that did the little fantail in, it was the
fact that even tropical fish rated for community living, will sometimes
shred the fins right off a goldfish.

Speaking of goldfish and climate, I've settled in Europe now and
preparing to keep some goldfish in a big tub on my balcony. I know
nothing about overwintering. If it gets near freezing (but usually just
above) in winter, how should I go about reduced feeding, etc.? Can you
actually keep them in a big tub (50 gallons?) in this kind of weather?

I do. I keep a stock tank heater floating in it and during times of extreme
cold, plug it in twice per day for 15 minutes. Keeps an opening in the ice,
yet doesn't over heat the tank. If you can afford the electricity you could
keep it plugged in all the time, as they do have primitive thermostats on
them. If you look on my website below, click on *My Pond Photos* and go to
Page 8, bottom right. This is my "little tub" using just an air stone, but
that was when the temps went down in the teens. I use a stock tank heater
now.

One caution: Unless you can afford to keep it plugged in all the time, only
plug in 10-15 minutes, else you can over heat the pond, and when you
unplug, and the temps drop, you'll have a tub full of goldies with ick.

~ jan http://users.owt.com/jjspond/

~Keep 'em Defrosted~
Tri-Cities, WA Zone 7a
To e-mail see website