Goldfish tail problem

Question
QUESTION: I have two gold fish for now about 4 months. This is the first time I have ever had a fish at my home. Both of them were doing fine till recently I noticed that the smaller one lost a big part of its large and magnificent tail.The top half is almost gone while the bottom stays. I dont know the reason for it.The fish did not eat for a couple of days but now it seems ok with its swimming and eating. Please let me know if i) the larger one is biting the smaller one ii) is it a disease iii) how to take care of it and iv) will the tail fin grow back again.

Thanks in anticipation

Ashutosh


ANSWER: More than likely, the fish was attacked by the other one. Whenever you know that you won't be around for a day or two, I might go down to the pet store and pick up a plant called anacharis, or elodea, scientific name egeria densa. That way they eat the plant, not each other. to fix it, I would get some melafix, and dose the aquarium with that until he heals up. It may also be some kind of a disease, since I can't see the fish I can't be sure, but the best thing to do with most diseases is just do regular water changes, and give him a salt bath. Don't do that first though, try the melafix, see if it helps.

---------- FOLLOW-UP ----------

QUESTION: Thanks for the advice. But as I said that the fish seem to be doing fine now (accept for its top half of the tail gone), should I use the Melafix or it would have any adverse affect. Further the other fish is also in the same tank. I hope Melafix does not have any bad affect on the healthy fish.Also will the tail grow back again?
Another thing which I wanted to know is that I have this habit of dipping my hand in the tank and one of the fish (smaller one) comes and nibbles with it. It swims through my fingers and seems to enjoy it. I am not sure if it is good for the fish as I have read somewhere that we should not be touching the fish. Please advice.
Sorry but dint mention the details of my tank earlier. I have a 10gallon tank with 2 goldfish which I believe are about 7-8 months old. I change the 25% water every week and 80-90% water every two weeks. I feed the fish once a day.Sometimes twice or thrice when they demand a lot. (I believe they demand it as when they are hungry they come to the surface of the tank towards me and swim rapidly. Also make splashing sound in the water).But most often it is once a day.

Answer
Melafix will not harm the other fish. The tail will grow back if you use Melafix.

Touching the fish shouldnt really do too much to them. Technically, the slime coating that is their immunities could rub off or something, but goldfish are pretty hardy fish, and I wouldn't worry too much about it.