A dying goldfish

Question
My aunt had three goldfishes in her pond. The water started to get contaminated with trash so we took them out as soon as possible. Now the fish are in a 10 inch long and about 7 inch tall tank. Quite small...

One of the goldfish's is having trouble breathing and is swimming sideways...and it's craving for air.

I don't know what to do. They grew up outside naturally... I don't have any fish food. Just a plastic tank and three desparate fish.

Answer
Hi,
This is a very difficult situation. They need a tank of at least 150 litres, or get them back in the pond. I would risk putting them in the pond, as long as you do huge water changes very often, as they will suffocate in a tiny tank like that without a decent filter.
if you can't get them in the pond in the next few days, but some flake food, a couple of fake plants, a bit of gravel, and if possible, a little filter. It won't have any bacteria in it, so won't be very effective, but will be better than nothing at all. Do daily water changes of 50 percent, using a dechlorinator and a nitrite remover in the water you put in the tank.

I hope very much that they survive,
Kathryn