my lionhead goldfish appears to have some little white spots on his beautiful long tail.. i would appreciate if you could tell me what should i do, in case this is a problem. thanks a lot!

Sounds like ICK.
Go to the local pet shop and get something called Quick Cure or another similar product for parasites.

Typically caused by strees (small tank, too much light / activity, overcrowded or poor water quality). Ick is typical but does not "attack" fish until they become stressed or malnourished. Very common for goldfish purchased from big box pet stores.

While at the pet store pick up aquarium salt and put in a tablespoon for every 5 gallons of water. Goldfish benefit from a saltier water and ICK does not thrive in water with any level of salt present.

Thanks a lot. I now observerd that maybe it't tail is somehow degrading a little bit, and it has some kind of redness on the artery of the fins. Does it have any relevance?

Hi, roxanazapartan!

Your sort of question has also been addressed a number of times on this site. If you look for links to other, similar questions on this page, either at one of the sides or the bottom, you'll find the threads. You might want to also click on them to see what additional information is available.

Thanks!

Actually, maybe I should say that I have two goldfishes. One lionheaded and one silver, much smaller than the other one. The little one doesn't seem to have any symptoms, only that he is keeping compay to the big one, on the bottom of the tank (which I had also observed as something wrong, they are usually very active fish)