Fish Changing Color

[Tdog]

I just got my first fish 2 weeks ago. I'm still very new but have tried to read as much as I can. I have one betta and 3 julii cory catfish in a 7 gallon tank with a filter and a heater at 79 degrees. The betta was completely blue when i got him, but has been turning kinda red the past few days. Is this normal? I tried to take some pics which you can view here.
Thanks!

 

 
 
Thank you!

 

[mark4785]

Hello,
 
Have you tested your water for toxic waste such as ammonia and nitrite? Also, did you dechlorinate your water with a good water de-chlorinator that removes both chlorine and chloramine such as Tetra Aquasafe? 
 
Reddening of the thins, gills or main body can be caused by an ammonia or nitrite level above 0 ppm and the presence of chlorine/chloramine is also an irritant to fish.
 
My suggestion to you is to test your aquarium water using an aquarium water testing kit, preferably the kit named 'API Master Test Kit' for freshwater aquariums, and to inform us of your aquarium's ammonia and nitrite levels.

 

[Ninjouzata]

It is pretty normal for their fins to change color Regardless it'd be good to have a test kit and test your water as above in case you think something may be off in the future.
 
Also, I know it doesn't relate to your question, but this size tank is too small for the julii cories and they should be kept on sand. They're also best kept in groups of 6 or more