Hopefully that will be enough. It's hard to tell how long. He's big and has a long digestive tract. It might help to offer him plain water to push the flush on down. Don't force him, just make the water handy.
Do you have him in a place that's protected from possible fire hose diarrhea? It may not happen, but it pays to be prepared so you aren't scrubbing poop off your walls.
Another person had to do this for her chicken, and even though she was warned, her bathroom suffered from a diarrhea tornado.