Strange goldfish behavior

Question
My goldfish has Popeye, and I've been giving him medicine (Maracyn TC & this penicillin stuff that he is supposed to eat). His eyes aren't as popped out as much as they were a few days ago. He lives all by himself in a ten gallon tank and I have a filter and I've tested the water and the PH is always at around 7.0, and the ammonia, nitrites, and nitrates are all fine, but my goldfish is acting weird. Yesterday he started swimming near the surface of the water. Normally when he isn't feeling well, he hides under his plastic hollow log. He also isn't eating. normally he 'inhales' any food I put in for him. I normally feed him every other day. (that's what a worker at petco said to feed him) He is also clumsy. He'll swim into the side of the tank and dart around. occasionally, he even goes to the bottom of the tank and then swims up vertically and almost jumps. He keeps his dorsal, pelvic, pectoral, and anus fins all the way out.  He also had ich a week ago, and that appeared to have cleared up. I think that the Popeye is a secondary infection. Also, Every once in a while  he tries to swim 'into' the gravel. Would you have any idea as to why on earth my fish is acting funny? How can I get him to eat and behave normally again?

Answer
Hannah,                                                                 First lets get rid of the popeye. You are going to have to do a 30% water change. Go get marycin 2. Treat your water. Don't forget to take your filter carbon out. Treat for 7 days this should clear up the popeye. Do not feed him for the first couple of days then feed him a couple squished up peas 2 times a day for a couple of days to release any gases that may have built up in his system. After the 7 days new filter carbon and a 25% water change. Then you should be feeding your goldie 2 times a day lightly. You can still give him a pea once a week. It is like a natural antibiotic for your goldie. You can also go to your local pet shop and get a veggie clip and once a week give him half a thin slice of orange. Face the meat out and the rind in. It is high in vitamin C and he will love you for it. I would also add some aquarium salt to your water. It is cheap ....1 tblspn per five gallons. The way they drink is by absorbing and releasing water. Salt helps him do this more efficiently. When you do a water change just guestimate the amount of water you took out and replace the salt accordingly. Remember salt is mineral and does not evaporate.....so it is only replaced when you do water changes....Good Luck,Tina