The net should be at the top as the shrimp are attracted to the light. If you listen closely you can hear them yelling "Go toward the light". I would not put live rock into it as it needs to be removed to clean occasionally as algae will grow on the mesh closing the holes. I have two models, the larger one is also a hatchery where the eggs are added each day with an auto feeder, the smaller one, I hatch the eggs first them condense them wit a net and pour them in. I use the smaller one every day and have for years that is how I keep my mandarins spawning and my pipefish smiling.