TLDR - Our Comet lost an eye quite some time ago due to poor water quality (we think) and it's recently gotten weirder. Pics at end of post.
About 10 years ago, my wife and I won two comet goldfish at a state fair. We got a ten gallon tank initially and didn't know anything about fish. We added a couple of others and over time, one of them died as did the others. Two remained, one comet and one albino pleco. About five years ago, they were too big for the tank and we had serious problems keeping the water parameters where they should have been. We still didn't know anything about fish at that point. Our comet's eye started to go cloudy and we treated the aquarium for several diseases as instructed by the pet store. I got my first master water test kit and the ammonia was way off, ph was super acidic.
We got a new 20 gallon tall, still probably too small, but we plan to upgrade at some point. Over the next two years, the eye scaled over and healed. We knew the eye was gone. About a year ago, the scales over the eye came off leaving a socket. I tested water and I was in the normal range for everything. No ammonia, PH was perfect for goldfish per the internet, and there were no nitrites and low nitrates which I corrected with a 50% water change. I do semi-regular changes with bottled ro water as our city water is treated with Chloramine and I just want to be as safe as possible.
About 6 months ago, our comet's eye (or lack thereof) started looking inflamed. I tested the water and found the PH went acidic for some reason. The ammonia started to go up and kh and gh were not where they should have been. I figured it was the water changes and missing minerals not buffering the ph. To make sure we still had bacteria, I got some Dr. Tim's and did a massive water change, adding back in minerals and leveling the PH at around 7.5. I reduced ammonia to 10 ppm (just so the new bacteria would have something to eat) and over the next week, everything seemed fine. Our fish's eye, however, had a fleshy protuberance. The following two weeks I was out of town and my wife let me know the growth had gotten worse. I got home last Friday and found a horn like growth coming out of the socket. Water tested fine. About two hours after I got home, I went to take a picture of it and it was gone, just an empty socket. I found the growth under a rock and pulled it out. It was fleshy and red, like a tumor had grown and come loose.
I am attaching pictures of the eye socket now. It looks gruesome, but she still seems active and is swimming fine. Water parameters are still in good shape and the pleco is fine. My primary goal is to find out what, if anything, I can do for our comet. Any help or advice is appreciated.
About 10 years ago, my wife and I won two comet goldfish at a state fair. We got a ten gallon tank initially and didn't know anything about fish. We added a couple of others and over time, one of them died as did the others. Two remained, one comet and one albino pleco. About five years ago, they were too big for the tank and we had serious problems keeping the water parameters where they should have been. We still didn't know anything about fish at that point. Our comet's eye started to go cloudy and we treated the aquarium for several diseases as instructed by the pet store. I got my first master water test kit and the ammonia was way off, ph was super acidic.
We got a new 20 gallon tall, still probably too small, but we plan to upgrade at some point. Over the next two years, the eye scaled over and healed. We knew the eye was gone. About a year ago, the scales over the eye came off leaving a socket. I tested water and I was in the normal range for everything. No ammonia, PH was perfect for goldfish per the internet, and there were no nitrites and low nitrates which I corrected with a 50% water change. I do semi-regular changes with bottled ro water as our city water is treated with Chloramine and I just want to be as safe as possible.
About 6 months ago, our comet's eye (or lack thereof) started looking inflamed. I tested the water and found the PH went acidic for some reason. The ammonia started to go up and kh and gh were not where they should have been. I figured it was the water changes and missing minerals not buffering the ph. To make sure we still had bacteria, I got some Dr. Tim's and did a massive water change, adding back in minerals and leveling the PH at around 7.5. I reduced ammonia to 10 ppm (just so the new bacteria would have something to eat) and over the next week, everything seemed fine. Our fish's eye, however, had a fleshy protuberance. The following two weeks I was out of town and my wife let me know the growth had gotten worse. I got home last Friday and found a horn like growth coming out of the socket. Water tested fine. About two hours after I got home, I went to take a picture of it and it was gone, just an empty socket. I found the growth under a rock and pulled it out. It was fleshy and red, like a tumor had grown and come loose.
I am attaching pictures of the eye socket now. It looks gruesome, but she still seems active and is swimming fine. Water parameters are still in good shape and the pleco is fine. My primary goal is to find out what, if anything, I can do for our comet. Any help or advice is appreciated.
Somehow it could have been the bottled water you were buying; I’d make sure to use a dechlorinator just in case. Anyhow, do you have any decorations that could lower the pH of the aquarium? Sea shells and unknown rocks that you may have bought could be messing it up... 
