Yes pic #1 is definitely Colombian Shark, and yes they need brackish water while young and full salt when mature.. I hope u have a separate tank because u wont be able to keep all those fish together due to salt needs of this fish.
Also the figure eights against the side of the tank ur talking about, its normal.. that's all they do lol.
Also the figure eights against the side of the tank ur talking about, its normal.. that's all they do lol.
