Found this info.
Keeping the fish in a small tank without filtration requires a lot of maintenance and can be frustrating. If the tank does not have a filter, nitrogen based toxins build up which can severely harm or even kill your fish.
I would advice you to switch to a bigger tank with a filter and until you can afford one, here's something I would advice
1. Feed them only ONCE per day and only the amount of food they would eat in a minute or two. They will survive on only one meal a day.
2. Get a food that is rich in essential vitamins and nutrients (This is important). Would recommend Flakes - Feed the fish only a little amount. Approximately 5-pieces of small flakes.
3. Do a water change twice daily and when doing a water change, get the fish out of the tank and place them in a bucket with water that is of the same temperature as of the tank
4. Get any residual poop or food up out of there before the fish are placed back in the water. For if you do not, you are defeating the purpose of changing their water.
5. Check the water temperature, by all means. A good mixture of hot and cold water is excellent. Not too cool, but not too warm either.The fish would die if the water is too hot or cold. I would say right around room temperature - between 20°C (68°F) and 22°C (72°F). And make sure that is maintained.
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Check your water parameters. Ammonia, nitrates and nitrites and even the pH, my goldie did that because of a spike in the ammonia and the pH was getting to high. If those are good, try feeding it some frozen, peeled peas. It helps their digestive system if its clogged and that could be weighing her down