YOu will see a bit of a cycle, but YOu can use a product like "The one and only" ?? anyway its a bacteria in a bottle product that will take up any N that you get from exposing the the rock. As per the sand its down to personal choice, both ways comes with pros and cons and both will need active husbandry to maintain for the long term success of the tank. With the no sand you will need to stay on top of detritus that falls out onto the tank floor, its pretty easy a you can control it fairly well with flow but you need to be actively removing it. With the sand its always becomes a matter of maintaining the top layer (reducing the load and keeping it airated) also at some point down the road (depending on bioload) you will need to deal with the end product that builds.
For me I hate the issues that sand brings to the game, BUT I do like the look of it, so I went with just a couple of inches and then maintained it by syphoning out as much detritus as I can so that the pressure on it is lessened.
On the rubble I find it to be counter productive, It tends to trap detritus and does not deal with it. If you keep that area in the sump clear the detritus is very easy to remove.
Mojo
