I'm still feeding my fish due to the mild weather for this time of year in
the UK. They don't seem too bothered when I throw the food in, so I only do
it once or twice a week. Should I be doing it more often or not at all
until next summer?

I've also heard that a ball of some kind in the water will provide them a
vent for oxygen should the water freeze. Is this true?

Many thanks,

Steve