Again I just wrote on youtube so I will just copy paste the video description:
This is his old aquarium, where I put him while I'm changing his water, you can see his temporary vase in the background, the water was conditioning so I keep him in there for about 10 mins.
I just noticed his pectoral fins are also a bit strange, specially the left one, I'm going right now to the pet store to buy a heater that isn't coming with my aquarium so I think I will buy also some sort of medicine for his fins.
I saw that one that is for yellowish dust on the fins, this might be his problem, at least looks like it.
I hope he gets better. Wish me luck!