+1. I had mine in a relatively large-sized gravel with low light. They did ok, but grew upwards rather than across, like a carpet plant.
If you want a carpet plant with large-grain gravel, why not try a java moss mat? If you have a facebook account, search for Acumen Aquatics and have a look in her album. She has a 5 gallon (being published in a fish magazine soon) with a lovely java moss carpet. :)