I've had my Betta fish for over 2 years now. Recently his behaviour has been a little strange. He likes to bury his head in his rocks and stays there for most of the time. Even if I tap the tank or move it, he doesn't budge. The odd time he will come up to the top and stay there but he is not as active as he is used to. He's in about a 5.2 gallon tank, no heater or filter. I clean it often with water conditioner. Is there a way to help him? He is also panting while sitting at the bottom of the tank.