I went back to Petco to ask if I did anything wrong and buy a plant for Mango so he (decided he’s a dude) doesn’t feel lonely. The guy told me that whoever sold it to me should have known that my tank was too small. One should allocate about one gallon of water per one inch of fish. My tank is about a gallon. So Socks was probably stressed out about being so claustrophobic or something. That’s why he wasn’t eating and now he’s GONE FOREVER.
But I think Mango will be okay because Mango eats a lot and poops a lot. Mango seems to really like his new plant