Altering Color in Piranhas
 

I've heard you can darken piranhas as they get older by giving them a meaty diet of frozen foods, does anybody know a good frozen food for this?

I've never heard such a thing. Piranah have such a varied diet to begin with, anywhere from smaller feeder fish, crayfish, even mice as they get large enough... (they like live foods) and in all my years of piranah care, I have never seen a specific type of food alter their color.

What will alter their color is stress, changes in water quality, maturity, and spawning.

Thanks for the reply. Do you think maybe the temp could change the color?

Yes, temp fluctuations will also change their color... that is an indication of stress. The water temp should be stable at 76 - 78 degrees for piranah.

Both shrimp and krill will bring out reds and oranges.