Oscar fish changes color

[BoomOscar]

I bought the 180g tank because I knew its better than buying another one in the future but I think its big for my baby oscar as he looks like very small. I put some fake plants decoration and white sand to have some energetic look and he swims on it but sometimes he hides on the powerhead and hes cute (Idk if its a he/she but I prefer a male)

 

[Muni]

Oh, before I bought the baby oscar its been there like 1 week because a friend of mine told me to put the water as the bacteria or something will form and its helpful. Im sorry if I didnt know anything but Im willing to learn. Thanks!

Thats a fairly short time to be running before adding fish. Especially if you didn't use a Bactria starter or lots of filter media from an established tank.

Here's a little guide for starting a tank.

http://www.firsttankguide.net/cycle.php

Hope your oscar does well. Keep an eye on him. Make small changes if you do anything. Fish are fairly tough and can handle the water not being perfect right away but they don't like lots of changes like trying to adjust ph up or down really fast.

 

[Muni]

I bought the 180g tank because I knew its better than buying another one in the future but I think its big for my baby oscar as he looks like very small.

Starting big is the best way to go. Saves you in the long run and is easier to maintain. Also bigger tanks are more stable as the larger water volume helps.

Oscars can grow to 18" long given time and good diet. Be careful with any other fish you add in the future as Oscars will eat pretty much anything they can fit in their mouth. Do lots and lots of reading before adding any more fish.

 

[pocky]

My oscar turns green when he's scared (hiding) or when he's pooping and straining a big turd out. Sometimes in the middle of the night if I turn the room light on I can see when he sleeps he's green too

 

[duanes]

With 1 baby oscar in a 180, you may not need to worry about cycling, which in some cases can take 2 months.
Since you have a friend with fish, maybe you could talk that person into giving you a handful of wet gravel from their established tank, or a rock or something else that they don't mind parting with that's been in their tank a while (it needs to go right from their tank to yours, not let it dry out).
That handful of substrate or object will be covered in beneficial bacteria and help jump start the good bacteria in your tank, and eat the ammonia the oscar will continuously produce.