I am thinking about using soil substrate with a small gravel on top (or crushed coral on top). I am used to sifting my substrates quite heavily. Obviously when one is layering their substrate they can not sift the substrate or it will mix all up. And also, with some sort of carpet plant that would make it hard too. My question is, without sifting (cleaning) the substrate, isn't there a big risk of ammonia build up from uneaten food and waste?