Hi I really need help ive had my shark for about a month. he recently started eating every other day. I have fast swimmers so it's kinda hard to feed him. But today he was gasping for air and I've found him on his back twice. I've tested the water everything pretty much okay. just yesterday i changed the filters so i can't do water changes just yet, but idk what to do. it's 180 gallon tank the shark is about a foot. please help Idk what to do don't want to lose him not for the money but is but first shark.