In rec.aquaria.freshwater.cichlids Siegfried Baesler wrote:

I think you can improve the quality of your photos,
if you would use more creative means like framing of the fish (golden
section).

Golden section is rather hard to do when framing multiple moving subjects.
It's a nice theory, but much harder practice. I've taken photo classes in
the past and found some use golden section as a crutch anyways. It's not a
required thing for framing shots and sometimes looks quite unnatural with
certain subjects. Besides, these are all crops of much larger photographs
to make them small enough to put on a webpage. If I really wanted to, at
the expense of file size, I could recrop to have the main focal object in
a golden section, but I found that to be unneccessary.