Hi! What does his belly look like? It should be round- if it isn't, he may not be eating. This is common with those little guys, unfortunately. If you have room in your tank, I suggest getting 5 more for him to school with- they are schooling fish, and tend to be insecure in small numbers. If you don't have room for 6, do you at least have room for 2 more? As far as the lettuce goes, you need to weigh it down with something- a rock with a rubberband, a spoon with a rubber band, a veggie clip, any of those will work. They can be quite partial to raw zucchini, as well, but- otos not eating in aquariums is not at all uncommon, unfortunately. Do you have a lot of plants in your tank for him to hide in? They're pretty insecure- lack of plants and buddies to hang around with will make him less likely to eat, as well. Sometimes its just trial and error with these guys. I started with 6, 3 of them refused to eat anything I put in the tank (even with heavy plant cover), but the remaining 3 will even eat flake food scraps and algae wafers from the bottom of the tank. Some just will, and some just won't. But, yeah, try getting him a few friends, and some plant cover, if you don't already have it, and see if he perks up a little. It also isn't uncommon to actually never see them eat, though... they're shy. You can tell by looking at his belly if he is eating or not. He should have a bit of a round pot belly, if he is eating. If it is sunken in, he probably isn't.