Im looking to add a small grass bed to my tank. The idea is to lay about 20 of these small rocks about one inch in side and make a wall that they cant cross... and have the grass or whatever grow out around them. So what are some type i can use for this... Im planting is really small gravel. need something that has low lights. And that good enuff that my cons wont dig up... They seem to be breeding on the otherside of the tank.