Nice looking tank, the first pic was really nice. What camera are you using? Try bracketing the F stop settings in manual, do a series of the same coral on a tripod with each pic having a smaller F stop rating, start off low (L2-H20)and 1 setting up in each pic. You'll then see what the F stop settings actually do and how it changes the depth of fields. If your shooting macro then ALWAYS use the manual focus..