I had about 4-5 inches of sand when I set up my tank, but now it is almost gone in places by the glass. I want to add more sand because my stilts holding the rock up are all showing. They used to barely show. I know I need to add it slowly little by little, but what else? I have also noticed that I don't have anything crawling around on the sand any more like I used to. If I get live sand and put it in there will it replace the little critters too?