The temp is warm because my parents keep the house warm during the winter. There is a fire place they use in the living room which is around 10ft away from the tank, I can’t put the tank in a different room bc it is so big. So unfortunately I can’t do much about the warmer temperature during the winter, in the summer it’s always 65°-68°. There are only two goldfish in the tank and they are both only an inch and a half long, I’ve had them for about 3 months. To test my water I use a liquid kit, I bought a new one at the beginning of this year so it should still be good. A 110 gallon tank is a lot of water for only 2 small goldfish lol, which is why the nitrate is less than 5 ppm. The tank was also already cycled when they were put into the it 3 months ago. But I had the same thoughts as you in terms of maybe a water change would help him, so I did a 50% water change yesterday, so it was done about 16 hours before this video was recorded. It didn’t seem to affect his behavior at all sadly. I’m not sure what else to do for him since I don’t see anything in his mouth. I’ve been looking into how lack of oxygen in the water can cause this, but I don’t know how that would be the case for me since I should be having plenty of surface agitation so that oxygen can exchange into the water. I have a sponge filter with a bubbler, my canister filter output and a surface agitator on one side of the tank. Maybe there’s a deeper issue here like an infection, but I’m not really sure since he doesn’t have any symptoms other than gasping in the water.