This is my first time here but was hoping to get some advice please. I have one electric blue acara in with some red head tapajos,black phantom tetras and some red eye African tetra. Over the past few weeks I've noticed he's been doing this funny shaking in the sand and also tugging on the leaves of java fern and shaking.I understand this to be a matting thing but as he's the only acara in the tank it left me a little confused and wondering if there is something wrong with him. He seems to be the boss of the tank and I've never seen any aggressive behaviour towards him from the others. Some help on this would be grateful appreciated many thanks. ?