OK, so I separated my beardies about 2 months ago because I wanted to be on the safe side. Baltumins got the old 40 gallon tank, and I saved up and bought Mazais a smaller tank. I got an exoterra tank that's 24" by 18" by 12". It is pretty small, I admit, but Mazais is smaller than average (and so is Baltumins) and it's the same width as my 40 gallon tank. Both beardies are now 15", and about a year and 4 months old by now. People commented on my old post about the red lights--they are PAIRED WITH white household bulbs in each of the tanks. (and of course UVB bulbs!!!). And as for lethargy, my beardies are NOT lethargic. They are really active and alert, and I always see a sparkle in their eyes. Also, I let them both run around the living room and my bedroom every day, so they get plenty if exercise. Mazais has gotten much fatter and healthier now, so that's good. Plus, she's eating well now, and eating greens much better than BEFORE she began to not eat.