Goldfish problems

Question
I have one goldfish in a 30 gallon tank. He's not too big and I keep the tank relatively clean. I worked at a pet store for over a year but I don't know what to do with my fish. He first got fin and tail rot then it stopped, then popeye (its stopped), then his mouth literally rotted away and it grew back, he had dropsey and his head and body swelled up to the point he was so bloated he couldn't move his fins(it has gone down but has not dissapeared), then the skin inflated and became a huge bubble then it went back to normal but then all the scales fell off so one side of his body has no scales on it and the rest of the scales and mouth also look bloody? Despite that he is suprisingly more active and swimming around the tank normally (I think he eats but is still thin) It's been over a month and besides cleaning I just don't know what to do anymore (I think I stress him too much with the melacyn and water and tempature change, is there anything left I can do or is this burst of energy just the last bit of energy before he dies? I love my fish and every day that I wake up to see him alive gives me a little hope but is that to good to be true?

Answer
Sounds like the little guy has been through a ton, its amazing to hear he is still alive. I completely understand how you feel, any fish can be just like dogs and cats, we get very close to them and only want the best for them. First, when you say temp changes, how does this happen? This is definately something you need to prevent. If you have to do water changes for any reason, make sure the replacement water the the same temp as the tank water. Yes, it may take more time and effort but it will be way less stressfull. Just get the cheap floating thermometers and take the temp of the tank and then run the tap water to the right temp, holding the thermometer under the running water until its the right temp. Also, I would recommend getting a different treatment. Yes, Melacyn is very good but as you mention it can be very stressful. I would get a more basic treatment, but make sure it covers all the diseases and parasites you fish has had and still has. Treat with that new product after doing the proper water change to remove the appropriate amount of the left over treatment. Follow the directions for the new treatment exactly, including the water change and dose. Other than these ideas, all you can do is hope he makes it. Its amazing he has gone this far. Just try not to stress, keep stable water temp, and get a newer less harsh treatment. With any luck, he just might survive. I hope this helps. Let me know if you need more help or have more questions.