resistant goldfish disease

Question
stats:
1. 10gal tank
2. 4 goldfish (2.5 inches each approx not inc tail)
3. fed alternately flakes,pellets,tubifax worms
4. aquaclear 20 filter
5. tank very biologically established (clear water w nice algea growth.
6. amonia non existant to very minimal.
7. 1/4 to 1/3 water change every two weeks & add aquaplus
One of the golfish has had a problem for almost a month but is still eating and swimming. (the other 3 are quite well)He has 2 small isolated white fuzzy spots on one side and one on the other side. These spots are protruding from his body somewhat.Looks like his sides are a little lumpy from the inside out.(sorry don't know how to explain it better). I first tried him on maracide and white went away but he still looked like he had some lumps pushing out from the inside. Within a few days of stoppin treatment , the white fuzzy spots were back.(ps.I used to work in an aquarium store and this is definitely not ick). I then tried marycyn two. The white almost completely cleared but again returned in a few days. I now have him on melafix. He's been on it 6 days and it seems to be helping minumully (one of the white spots is gone,but it looks ulcerated there). Could it be internal parasites with a secondary fungal or bacterial infection and that's why its so resistant ? I'm a fan of Mardel products. Should I be using two products together ? Whats my best combo to treat bacterial/fungal and parasitic ? Thank you for your time. I know goldfish are the "mutts" of fish, but I really love my little buggers.  Treena

Answer
Treena,

 Well first off the tank is too small. One goldfish needs 20 gallons just for him and each added fish needs 10 gallons. They need to be in nothing less than a 50 gallon tank. Since the tank is so small you should be doing 25% weekly water changes. Have you tried medicated food? Remove the sick fish and put him in your hospital tank. I have included a website that I think will help you out. After reading it and trying what they suggest and your fish is not better or he gets worse let me know.


http://thegab.org/Illness-and-Treatment/medicated-food-explained-and-explored.ht...