Howdy folks. I have one goldfish in a 30 gallon tank named Fillipo. He(?)'s about 6 years old. Found him abandoned in a tupperware dish : ( . He had one friend who didn't survive past the first couple hours after I found him. I think something may be wrong with Fillipo but I'm not sure. If someone could offer some suggestions (or even just tell me I'm worrying about nothing) it would be greatly appreciated! He has red areas in his tail and along his back just forward of the tail. His fins are ragged. The spot where his pectoral fins join his body are dark red/red. Also he's swimming erratically - every once in a while he will dart around the tank like something freaked him out, bumping into multiple walls or the bottom of the aquarium. What's more, some fuzzy, stringy, white growth or slime has started appearing on my plastic plants and the filter intake. On the plus side, he doesn't look that bad. I'm not actually entirely sure he's sick. He still eats and swims around, but I want to see what people with more fish knowledge than me think. Events leading up to this point: About two months ago he got popeye, which I treated with Furan 2. He healed up quite nicely afterward. About a month ago, I decided to change out a good portion of water as well as remove some of the gravel. Taking the gravel out kicked up lots of detritus though and made the water cloudy, so I stopped. I also removed most of my plastic plants/other decorations, dried them off, then put them in a shoebox. A week later I noticed a red patch at the end of his tail and started keeping an eye on it. I made some water changes after seeing the water quality could use improvement. The chemistry has fallen within safe ranges after that every time I've checked the water. Brown algae (?) started appearing on the sides of the tank frequently enough that I felt the need to wipe it off around the same time. There was not a lot of it. About two weeks ago, I thought I noticed the development of the red area along the back. Last week the red area along the back grew more distinct, so I decided to go to the fish store and ask for some advice. I walked out with some erythromycin. I also bought some marine sand. Over the course of the week I removed gravel from the aquarium and let the detritus clear up before continuing (during this time I frequently rinsed out the carbon filter pad), then I rinsed the sand and placed it in the aquarium, and re-added some of the plastic plants I kept in the shoebox. There has been no brown algae since then. Shortly thereafter the pectoral fin joints started looking abnormally red/purple (or perhaps I just never paid them any attention, maybe they're supposed to look that way?). He seemed to be happy with the sand, he rooted around in it like he did the gravel and swam around doing fish things. The next day I began the erythromycin treatment (4 doses with 1 dose every 24 hours, 25% water changes before the third dose and 24 hours after the fourth). He was showing signs of irritation prior to the first treatment including darting around the tank. Water chemistry looked fine, an ammonia test strip matched the lowest value on the chart. On the third day of treatment, while I was changing the water, I noticed the white stuff on the plants. Not sure if it's bacteria, fungus, fish mucus, fibrous material from the filter I kept rinsing, or what. It was slimy when removed from the tank. Today was the last day of treatment. The white growths were larger, I removed the plants and rinsed them/wiped them off, and attempted to wipe off the filter intake. If my fish has something it has been largely unresponsive to the erythromycin. His tail fin has improved slightly, there is a thin white area between the bloody area on his tail and the tip of the tail now. The red area by the base of the tail has not improved, the pectoral fin base seems to be slightly more red than it initially was. He is still darting around the tank and slamming into the walls/sand every once in a while. Of course, all that being said, it's hard to judge these kinds of problems without seeing them, so I have also taken a lot of pictures. I tried to highlight some of the problem areas. View attachment 20160628_191605.jpg View attachment 20160628_191617.jpg View attachment 20160628_191625.jpg View attachment 20160628_191646.jpg View attachment 20160628_191702.jpg View attachment 20160628_191704.jpg View attachment 20160628_191708.jpg View attachment 20160628_191714.jpg View attachment 20160628_192439.jpg Some the pictures are sideways apparently. Well alright then. Anyway, what should I do? Thanks for reading.