This is my halfmoon king betta I got from petco. Currently he is alone in a 10g tank (which might even be a little too small for him when he's fully grown- he's ~3-4" right now, which is quite large). He occasionally (albeit rarely) will "flash" his fins and make the full halfmoon shape- it's awesome, but almost impossible to get a photo of!
I was originally at petco to pick up a female swordtail and had an extra 10g tank with a heater and an AquaClear filter at home. I saw him and sort of impulse bought him- but my brother has 3 other bettas who are all doing well so I figured why not!
Whenever I do maintenance in the tank, he sort of tries to swim between my fingers. It's cute but a little bit creepy.

He also begs like a puppy for food- I love his personality! He really seems to like moving between my Japanese Rush (Acorus Gramineus)... whenever he slightly touches one, the parts of the plant outside of the tank rustle!
He doesn't have an official "name" at this point, but I have nicknamed him Koi because he looks almost like a mixture between a regular betta and a koi.
I was wondering if I should give him any tankmates or not... does anyone have any suggestions on what might make some nice tankmates (if any?)? I'm worried he could attack little fish, but he might just be a gentle giant.

Hopefully I'll get some more photos once I finish learning how to work my camera!