The goldfish has excess mucous on its fins. This is normally caused by poor water quality or a low pH.
The fine airbubbles are bad for fish and need to be turned down a bit.
The tank water looks cloudy, which is usually associated with uneaten fish food or a filter that has not established yet.
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Check the water quality for ammonia, nitrite, nitrate and pH.
Do a 75% water change and gravel clean the substrate every day for 2 weeks.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Add 1-2 heaped tablespoons of rock salt, sea salt, or swimming pool salt for every 20 litres (5 gallons) of tank water. Keep salt in the tank for 2 weeks.
When you do the daily water changes, add salt to the new water before adding it to the tank so the salinity (salt level) remains stable.