After a water change and a change around in the tank to get rid of some old plants and algea my largest snake head has started acting strange he goes up for air which is normal but for some reason he holds his head out of water and moves around the tank he has never done it before little worried tbh I thought water condition but the other snake head in with him is fine and acting normal there pair off so no fighting or anything any ideas would be appreciated its a 1200X500X500mm tank size