dark blotch

Question
I have a 9-inch Albino Oscar who has just been moved into a 55 gallon from a 10 gallon.  Lately I've noticed a large, slightly dark blotch on his head and I'm wondering what this could be. He has black-tipped fins and I'm not sure if this blotch on his forehead could just be his coloration or if it's something I should be concerned about.  He has an excellent appetite and is usually pretty active. I have never seen him dig in the gravel. He shares his tank with a gold gourami and they are both separated from a few tetras, danios, and barbs by a tank divider.  These fish only occupy about a quarter of the entire tank. There are also two separate filters with bio bags and a few live plants. I generally keep the pH on the acidic side--usually around 6.4. I'll admit that I'm not too great with keeping up with water changes and I honestly don't change the bio bags often. Maybe this has something to do with it. Any help would be great, thank you.

Answer
Hi Aaron,
 It could be a bit of a bruise.  Take it as a warning though that maybe you should be doing regular water changes so that if something else happens you can rule out "lack of water changes" as a possible cause :)

-- Ron
  rcoleman@cichlidresearch.com
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