Last night after I feed my bettas and turned the light out, I noticed that one was resting under the filter at the back of the tank. His fins were up and he was kinda propped up. I just figured that he was sleeping or something. This morning, I found him in the exact same spot. He was okay because I stuck something in the tank to see if he moved, and he dashed forward as if startled. So do they sleep like this all night, or do they come up for air? He had a craft mesh hammock/tube that he swims through, but I've never seen him rest in it. He also has a cave. Do I need to offer them more things to rest on at the surface?