carbon in the filters gives the water a more "clean" look, if your shooting for darker water, there is a product (cant recall the name right now) that you can get from any pet store and you can put it in (read instructions) and it will give your water a murkyer effect. like amazon type. water will go a bit browner etc... ive never used this product before. if you do plan on using it make sure take the carbon out of your filter because it will just catch all this and what not. if you want to dim your lights grab some white hockey tape, and double layer the light, i did this on my old tank and it brought the brightness down