Anyone know what type of fish this is?

[CFQTPye]

My LFS had these fish in their tanks and I've never seen anything quite like it. It looked as if their fins were actual seaweed. I'd like to possibly add one of these to my tank one day but want to do the proper research first. Any takers?

 

[evolved]

Selene vomer (Lookdown) juvi. They are only like this in the juvenile stage and become HUGE as an adult; need a massive tank.

Threadfin Lookdown