Goldfish depression?

HI new to forum because I need some help. Sorry if this is long. I have 2 fancy goldfish in a 10 gal (oranda and lionhead) Got at same time and were same size but the oranda is now triple the size of the other. He has been a bully and especially around meal time. To the point where I had to overfeed so lionhead could eat. Tank was always cloudy. Noticed a lot of white poops from lionhead and that he was often hiding. Decided enough was enough, set up another tank for him. But after removing him, the other fish seemed to get depressed and quickly say fins get ragged. (Similar to after I first got them. Which then I cured with fin and tail rot treatment) He also stopped eating. Started just hanging at bottom of tank. After about a week of the other fish getting well fed, I put him back in. Hasn't really helped the oranda. I thought it was stress or depression. But could it be something else? I tested the water, it is fine. Thoughts?

 

10 gallons is way too small for goldfish. I have a feeling they're producing too much waste for the tank to process, leading you with high ammonia and or nitrite.

You say you've tested the water, what does "fine" actually mean?

You have 2 options IMO, rehome the fish or upgrade to a bigger tank and keep water quality pristine.

 

Goldfish are social and do best in pairs or groups. Due to the size of the tank I also think there might be water quality issues at play. Could you fill out the emergency template?

 

Thank you for your feedback. I tested for ammonia/nitrates, gh, Kh, ph. All were at safe measurement fir goldfish according to test. Again, the only thing that changed was I removed the one fish who was being bullied so much he couldn’t eat. Same exact water and process. I will fill out the template.

 

The only truly safe ammonia level for fish is 0. I have 3 goldfish in a 400 gallon pond and can’t imagine how you could keep ammonia low enough in 10 gallons.

 

It is 0

 

the nitrogen cycle can handle ammonia and nitrite as long as there's enough surface area on the filter media to grow enough bacteria.

its the nitrates that's the problem. 1 ammonia turns into 4 nitrate

as you've figured out lionhead/ranchu are generally small, and oranda are usually large.