I have a Fuji Finepix S7000.
The settings are different depending on what I want to take a snap of. The settings also depend on the amount of light that you have in your tank. The more light the faster your shutter speed can be therefore the clearer the image and the easier it is to get a descent photo.
If you have low light then, this generate a problem as the shutter will need to be open for longer therefore increasing the blur in the picture if the subject or camera is not still. This makes it a lot more difficult to get a good snap of the fish. Thus they have to be literally motionless and as you are most likely aware this is not something that Africans do often. This is why some people require the additional use of the flash.
For up-close pictures I turn off the flash, turn on the macros (super macros of you have it), turn the shutter to between 60 and 40 and then take stacks of photos. (god bless digital cameras) From these stacks of photos lets say fifty, maybe 5 would be OK.
I am of the opinion that photographing fish is a numbers game and you will eventually get a good one.
tanks