Both pictures are the same Oscar. I was hoping someone can tell me if it normal for him to change colors like that.
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As far as I know, oscar fish do not change color unless the water is bad, ammonia or nitrite are present and/or a large change in pH in your water (you need to take a water test to be sure about this).
Some types of carp and plecos can change color if there is a change in the pH of the water. If plecos are stressed they looks almost grey.
Carp fish can change color in a radical way if the pH changes. Goldfish and koi can lose all of their color when the pH changes (after buying koi I have seen orange koi getting totally white in less than 24 hours), but the color will return to normal when the fish have adjusted to the new water.
Many types of fish can change color if they experience stress, changing temperature-pH-ammonia-nitrite or simply by getting disturbed when you clean their tank.