Why are both the top part of my goldfish's head injured?

Question

I bought a beautiful 3 inch Orando Goldfish into my 20 gallon tank since my Fantail seemed a bit lonely. It's been 2 weeks now and for some reason both of them have injuries to their heads. I clean the water regularly, am I doing something wrong?

Answer 1

The fantail may be nipping at them to show that the tank his his territory. I'm guessing you were not told to rearrange the tank before putting them in so the best thing I can suggest it that you temporarily take all of the fish out of the tank, move stuff around, and put them right back. Fish are not the smartest and goldfish are at the bottom of the smart fish list so to them, the tank will be a new one. The first fish you had in there will not feel like he needs to attack them and show that the tank was his first because it will be like a new tank to them. Try it out. Good luck

Answer 2

newly bought fish should be quarantine, the problem is the new fish carry the disease in the petstore you just add it in your healthy tank.  It is a standard operating proceedure to quarantine the fish first before adding it to the main tank.

kOi keeper & goldfish keeper

Answer 3

You are keeping 2 goldfish in a tank that is too small. They are probably attacking each other because it is too small and they are getting territorial. Return the fantail or get a bigger tank. This isn't going to solve itself.

EDIT:

Actually goldfish are quite intelligent. http://www.underwatertimes.com/news.php?...

The moving of decorations just breaks up established territories.