Red or black Pacu?

[pacu mom]

That is definitely a red belly.

I agree. Many red bellys lose their red color as they get older. Here's a pic of one of mine:

 

[pacu mom]

OP: unless you have the means to build/buy a massive (800+ gallons) indoor pond/aquarium, get rid of that thing ASAP. It will outgrow anything else and will be a nightmare to care for in a few years. And it will be much harder to get rid of as it grows.

We have had our two pacu in a 300 gallon tank for the last 5 1/2 years. The tank is too small for them. We are now in year 3 of a big tank upgrade for them, i.e., we purchased the tank 3 years ago, and are building an addition just to house the tank. Pacu have the potential to live 30+ years in the right environment. When it comes to housing them, you have to go massive.

 

[QuentinT19]

have 2 red-bellied pacus, cant really know what they are once they have grown as the red colouring tend to disapperar as they mature.