This is Roger about 1 yr old. I had him in a tank with another axolotl but took him out cause he's not eating and has been floating. Previously the tank had gravel in it but i took it out about 1 week ago as i read they can swallow gravel. I dont know what is wrong with him but he looks very bloated and is swallon around the bottom. He also has black mould around his mouth and has lost most of his gills. Can you please help me.