Do you normally add salt or have you only just recently added it for this problem?
How often and how do you clean the filter?
How long have you had the fish for?
How long has the fish been swimming like this?
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The floating upwards can be air trapped in the fish's intestine. This is common with fish that are fed dry foods. Stop feeding dry food for a week and feed them frozen (but defrosted) or live foods. If the problem clears up after that, then it is air from the dry food. If it doesn't get better on frozen/ live foods, then it could be a swim bladder problem.
However, the fish's colour looks wrong and its tail keeps flicking upwards, which is weird. The odd colour could be the start of a microsporidian infection.
The tail flicking up could be the fish trying to keep buoyant or an external infection.
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WHAT TO DO NOW
Wipe the inside of the glass down with a clean fish sponge.
Do a 75% water change and gravel clean the substrate every day for 1 week. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in. It also removes a lot of the gunk and this means any medication can work on treating the fish instead of being wasted killing the pathogens in the gunk.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.
Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.
Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.
Increase the salt level to 2 heaped tablespoons of rock salt for every 20 litres of water. Keep the salt in there for 2-4 weeks. When you do water changes, add salt to the new water before adding it to the tank so the salinity (salt level) in the tank remains stable.
If there's no improvement after a week with daily water changes and salt, or it gets worse during that time, post more pictures and another video. When you film the fish, hold your phone on its side so its horizontal and the video fills the entire screen.