I've had my fair share of stunted fish over the years, one in particular that has stood out like no other.
I do not, for one moment believe he suffered while in my care. Obviously I can't say that about his life before I stepped in but at the time I had the resources and time to cater to his every whim and do absolutely anything he needed to continue living as comfortably and as easily as possible. I looked at like this: I can do all of the work, the hard stuff, and the easy stuff - so he can simply glide through his days (I was never sure when his time would be up because he was so fragile) and never have to exert energy on being anything but completely satisfied. He wasn't too weak to live with filtration but it would tire him out and I didn't like that because I knew it took away the energy he required to remain healthy so I worked around it by carefully doing multiple water changes, sometimes more than once a day, every single day without fail and never used a filter with him. I never used a net on him either, too stressful, so I would submerge a bowl in the tank and wait for him to swim in on his own (that sometimes took 10 minutes LOL but I refused to force him to do anything he didn't want to do!) I was sure to keep other goldfish with him because I don't like making fish live alone so I made sure he had slow moving, calm, gentle goldfish companions. I worked out a special diet and fed him usually by hand or with a tweezer because I wasn't sure how much vision he had. Sometimes I stayed up all night observing him and making sure he was eating enough and not doing anything out of the ordinary (he sometimes did back flips and while they didn't seem to affect him negatively in any way it was still weird looking and always made me nervous) I made sure he got time in the sunny window every day but stayed near by to make sure he was never distressed. I always liked looking at him in the natural sunlight.
It was a lot of work for sure, with not a whole lot received back aside from the knowledge that I was being a dedicated servant and honestly, it was one of the most rewarding things I've ever done in my life. He died very peacefully just over a year after I took him in.