Please help. Not sure whats wrong with Bob!

Question
Hi, please can you help-I would really appreciate some advice. I have a 19 year old goldfish which I have been told is part koi although I always thought he was a comet. He is living in an 80 litre tank. I recently went on holiday for a week leaving him in the good care of my flatmate, but when I returned he looked terrible. He has what looks like a fine dusting of flour and a vaguely flaking coating on his body. He also seems to have a shredded tail fin which I presume is fin rot and his other fins are flat against his body. He lies on the bottom of the tank not moving and looking miserable and at first was sometimes flying round the tank bashing into things although this has now stopped. I went straight to the aquarium shop who told me he probably had finrot and white spot and sold me Pima fix which I have today learnt only covers fin rot. I used that for two days but night before last found what looked like a fish leech on his lower fin. I removed it easily but I then spotted another one the next morning, that one came off easily too and I went back to the shop and they gave me Interpet no 12 anti crustacean and parasite. I used this yesterday but he looks no better and  don't know what else I should do. I have been given some conflicting advice by the 2 fish stores near me and I am really worried about him as he is quite a precious childhood mate. I can't work out what is wrong- the second store I went to suggested velvet but I am not sure and I can't keep on using different treatments as I now have to wait seven days from using the Anti crustacean and parasite treatment as it is so powerful-how long should this treatment take to work? I noticed today that his eyes have a cloudy covering on them which seems loose in places. I have had the water tested and it was fine and before I treated him with the pima fix I did a 50% change as instructed, then a 30% change the day after I used the no 12 Anti crustacean as instructed on the box as it said it raises nitrate and ammonia levels. I have today added a nitrate and ammonia fixer and put the pump back in having removed it when I used the No 12... I have also been using an air stone this last few days to keep things going without the pump. I hope this all makes sense, please email me if not. Any help would be much appreciated, I have looked a lots of web pages but don't know much about sick fish as he has always been fine so have not got very far.
Thanks very much for any help you can give.


Answer
Hi Lorna,
Thank you for your letter. I can see that you are very distressed and I will try to help. First of all, I do not recommend any aquarium supply shop pharmaceuticals, as they are expensive and usually just make things worse.
So, if you have a gut feeling about it and want to quit all the chemical treatments, go with it.
Your flat mate might have drastically overfed the fish, polluting the water, killing off the live bacteria culture, and causing disease.
Overfeeding is the most common cause of the type of problems you are experiencing.
Here is my advice. Buy a friendly bacteria culture like "Cycle." Ask your aquarium supply shop what they have. Stop all feeding and water changing for 24 - 48 hours. Add the friendly bacteria culture. Then, do small water changes to clear the water. Add more Cycle (or other bacteria product) with each water change. Use pure bottled water. Make sure the temperature matches what's already in the tank.
You may also use a little Stress Coat or other aloe vera product like Stress Coat, but don't use a lot and apply it directly to the fish.
My page on wholistic aquarium care has all the instructions here, print it out:
http://steamboats.com/aquarium.html
Write back and let me know how it goes.
I'll be pulling for you and Bob.
Nori