I have 5 clown loaches and they swam up inside a ornament in the fish tank. How can I get them out?

If they won't come out on their own, you can gently poke the ornament with a long stick to shake it a bit. If that doesn't work, be sure your hands are good and clean and reach in there and pick the thing up. Unless they are somehow stuck, they should come out. Is there something that is scaring them and making them want to hide? There may be other issues to resolve.