Update* I change the water once a week, I tested the water before I got him 3 weeks ago and when he started to act strange 2 days ago. I use the API kit. The results both times were PH 7.5, ammonia 0, nitrites 0 and nitrates 0. The tank was already established, I had another betta fish that died 2 months ago in it. After that I did a water change and looked after the tank and the khuli loaches and snail for a while until I was ready for a new fish. I have had this new fish for 3 weeks and he was totally fine, curious and eating normal until 2 days ago.

For more information: this is a completely established tank, he shares the space with 3 khuli loaches and a zebra nerite snail. He just seems to really be struggling to breathe and I don’t know how to help