You can't do a thing. If your ex is a couch potato and sits around watching TV for nine hours a day, allows your child to play games on the computer while he watches TV, this is what he does in his own home, his world, his choices.
He's a different person from you. The Courts are going to do nothing about it. He's not harming her, he's not abusing her, he's living his life the way he wants to. It's the same with the company he might keep -- his life, his friends, his choices.
I didn't particularly like everything my ex's household either, and our son stayed with him all summer, every summer until he was 18 or so. My ex's household was different from mine, and i accepted it. I didn't sit around dwelling on what my ex was doing at his house or how he was entertaining or "training" our son.
When our son was at home with me, he lived a different lifestyle and we were more active, he had more responsibilities in my home. He'd come home and be a bit bratty for a while (typical behavior for some children when they return from the other parent's home). But soon, he'd settle back in. He respected my rules, our lifestyle and the truth is, my son and i are much closer than he and his father could ever be.
Just be a good parent and good example.
I had things to do, and a life to live. And today my son is 28 years old, has his own child, and is no worse for the experiences he had with his Dad over his summer vacations.