Sony DSC-F707
The DSC-F707 is a pretty old camera, 7 years to be specific. You must be getting it used because Sony hasn't made any new ones for some time. The digital sensor's sensitivity only goes to ISO 400 which means taking pictures in the dark will be a problem. Contrary to logical thinking, reef tanks are considered dark subjects. Many newer models will include ISO 800, 1600, 3200, and on nicer cameras even 6400. The max shutter speed is 1/1000 compared to today's standard of 1/8000. This means taking pictures in bright light will be a problem. So you can't take pictures in the low light or bright light. It has to be just right. The only image format is Jpeg, which means the colors are your exotic corals will be off and there isn't much you can do about it. I would say NO.
Nikon Cool Pix 990
The Cool Pix 990 is even more ancient than the Sony DSC-F707, weighing in the Roman Census at 8 years. When you pick up this used camera make sure you asked how the previous owner stored it, as it may have fossilized rendering the camera useless. Haha just kidding but seriously, its way past its prime. I'm not even going to go into details as they are surely worse than the Sony counterpart. It does have one good thing going for it, in that instead of only Jpeg, the Nikon Cool Pix 990 can shoot Tiff format as well. It does look like a very awkward camera though.
This said I would recommend neither camera for pictures of corals and suggest you find something else you might like. Your prized possessions will appear discolored and unnatural in a best case scenario. This however would likely be the least of your problems.
Look for something that can shoot in a "RAW" format, as I consider this a necessity when colors and quality really count.
