Hi all,
After keeping them in the containers for treatment over night, 2 more belly up this morning but the rest are quite happier now so I have returned them back to the pond.
I have them for 12 years, the water always crystal clear with lots of water plants and sufficient bio-filters.
I really didn't know what to do when seeing them slow swimming, gasping for air at the surface, the waste came out from them were filled with white stuff (white bread) , I did some googling and lots of ppl advise do not feed fish with bread , Bread contains yeast and when eaten by fish, it will expand and can cause constipation. And in my case, the big golden one died with a swollen tummy, when I got her body out I did some squeezing on the belly and the waste came out with white stuff.
At the moment, they don't seem wanting to eat anything (stressed after being scooped in and out so many times I guess) so I don't feed them , just leave the air pump and the bio filter running and keep monitoring them. X my fingers that no more casualty in the next few days.
FYI, I'm leaving in Adelaide/Australia, it is just in mid-winter (roughly lowest is 4 degree C ) so the weather is just fine. So far 1 large female (45 cm) (the golden one above) and three mid-side (30cm) have gone.
Thanks all for the comments. I'll update in the next few days, hopefully they will be fine.