Hi, ya im thinking the same as you are that he probably just needs abit more time but I wouldn't let him go to much longer. They are all different, I have 2 that ate as champs the first night home and my third guy took him about 4 days to settle and eat. Just keep trying and if it goes to much longer you may have to try and force feed, but keep this as last resort because its very stressfull for them. Were is the gauge sitting inside your tanks? is it in the one with him or in the bigger one that the smaller is in? If its not in the small one I would put it there and see what the temp is, it may abit cooler in the small one and he may need a little bit more heat to get his metabolism going.