I swear my telescope goldfish's eyes are swelling. Also he has some marbling. I'm slowly adding salt to the water to help. And have a heater I could set up. I'm going to put the plants in a bucket. He lives in a thirty gallon but it has low filtration. I'm getting a second bigger filter for him on Thursday. (He lived in a 10 gallon a week or two ago) I tested the water with some test strips and the ammonia is good it reads 0. Nitrite is probably between 0 and 0.5. So a bit high. I'll vacuum and do a water change to try and lower that. He's been doing some surface gasping and his head and gills looked dark orange - red, and his tail possibly ragged. It's hard to tell it's my first goldfish. So I was concerned but not worried. However the change in eyes size which is pretty even on both has me worried.