Hey wuts up, I have a young bat ray that is about 1 foot long, fin to fin. I know this sounds strange but he occasionally gets a veiny bubble coming out of his anus. ha anus... But seriously, I've been noticing this when I feed him. It gets large and then small again, almost like a pulsating balloon. ha pulsating. But really, what is this and should I be concerned? This only lasts for 5 to 10 minutes and then its gone. I have been unable to find out why this is happening. Please help.