I don't know a great deal about fish, but do enjoy keeping them
I have a 120 ltr tank, I have 1 goldfish, 1 blackmoor and recently added a orangey.
Around 10 days ago I noticed the blackmoor always at top of the tank, I could see he would stuggle staying at the bottom, he'd swim down but keep coming back up. I've been doing regular 30% water changes and also cutting a thawed frozen pea in to bits after taking skin off.
I thought he was improving until today, when I came in from work he was on bottom of the tank really trying hard to stay there, but his back end kept lifting up. He has perked up abit over the last few hours and he's had some pellets.
Also my goldfish (which is smaller than him) went over to him a few times and went under him and was nudging him from underneath trying to get him moving.
I thought he was actually dying earlier, I was so worried, I still am. What could be wrong with him and is there anything I can do?