I'm using a Canon 50D and a 100mm macro lens.
My tank is pretty clear, actually I was just remarking to my wife the water is crystal clear but for one, the tank is pretty new, it's only about a month old now. Two, I only have one fish in there now, so the bioload is relatively low. I do feed him a lot but it's nothing the filtration I have set up cant handle easily. Three, I dont have anything in the water that leeches out any kind of color or other thing that affects water quality. A couple weeks ago I put in about 10 small pieces of live rock in one corner and that was it, otherwise it's all plastic decorations and a small 9lb bag of sand on the bottom.
When he digs in the sand, the tank gets cloudy but the filters get rid of it pretty quickly or it settles down again.