I think my fantail goldfish is sick!

[Angi]

I have seven golfish. They are all doing well except for one orange fantail. It just floats at the top of the water, it will swim down occasionally, but floats back up within a few seconds. It seems to be weak. It looks like it may be a little bloated, but it's hard to tell. The others are all fine! I have put it in a small tank for now, but I'm not sure what to do. It's not floating on it's side or upside down, so I'm not sure if it's a swim bladder infection or not. I got it about a week ago along with another orange fantail from the same tank. The other one looked a little puny yesterday, but is doing great after a 50% water change. This one seems worse! Please give me some advice! I really like this fish and don't want it to die!

 

[Angi]

I have seven golfish. They are all doing well except for one orange fantail. It just floats at the top of the water, it will swim down occasionally, but floats back up within a few seconds. It seems to be weak. It looks like it may be a little bloated, but it's hard to tell. The others are all fine! I have put it in a small tank for now, but I'm not sure what to do. It's not floating on it's side or upside down, so I'm not sure if it's a swim bladder infection or not. I got it about a week ago along with another orange fantail from the same tank. The other one looked a little puny yesterday, but is doing great after a 50% water change. This one seems worse! Please give me some advice! I really like this fish and don't want it to die!