After a few days, he's stopped laying down, but now he's only on one side of the tank, ironically the side with the heater I noticed. But I also noticed no real change in temperature. I heard the older they get, they stop moving as much? He's still eating, my nitrite levels were and are still off the charts, a lot of my plants were dead so I'm hoping that's why. I'm doing a 50% water change, I removed all my dead plants as well, and will probably put in a double dosage of prime / quickstart.