I had altums, and to me, they represented grace and stately beauty.
"Beauty will be convulsive or it will not be at all" was the old surrealist Andre Breton's interesting definition, and that makes me think about absolute beauties who combine movement and colour to amaze us. Iriatherina werneri, the threadfin rainbow is up there. A group of 5 or 6 Chromaphyosemion biteniatum circling each other and dancing off without biting each other is one of nature's great shows that fits in an aquarium.
We have dancing beauty, sitting there and staring back beauty, stately grace, impossible colour intensity (freshwater killies and many marine fish), "man" made beauty like Betta splendens linebreds - so much. I have keot little Enteromius jae whose redness almost hurts to look at, and seemingly electric blue Celebes rainbows.
I don't like to be smacked in the face by anything, including beauty. I like realizing how good something is after a few glances. That's why I would never include fish like linebred Discus on my list of beauties. I find the pigeon blood and similar fish outright ugly, though if you have one, I'll pretend to be impressed if you are.