My best results for corals generally has been with the pumps off, tripod, F8 (aperture priority mode). Get as close as the focus will allow (straight perpendicular to the glass), then crop the image on the computer. Pretty good results, but still not as good as some others that I've seen here. I set the WB to cloudy, I tried to manually set it and my results were lacking. I also play with the exposure bracketing.