the flowing fins in the top pictures are also known as meteor minnows, same fish just bred to have those nice fins (kinda like fancy guppies). from what I've heard the meteor variety is hard to come by and usually costs more since it doesn't seem that they are breeding them as much as they were (apparently people lost interest in the fish). also note that the differentiations are not due to captive bred vs wild caught because this fish is extinct in the wild. with the regular white clouds a good diet and water conditions will do wonders for them in terms of color and fins as with all fish. also note that these are very hardy fish despite extensive captive breeding (usually leads to small genetic diversity which leads to weak fish). sexing them as said is done by belly size, with females plumper and males skinnier. also be known that these fish have a reputation rivaling that of rabbits and they tend to avoid eating baby fry so you might be stuck with more fish than you bargained for eventually. to put this in perspective someone said that to breed them all you had to do was "just add water". also there is a minimum amount of 5-6 of these fish per tank since they like the company (schooling fish). I think that's about it oh, some people argue that white cloud minnows are a fast moving fish but I usually notice that they are only about the same speed as a platy, if this is fast it's more due to personal perception. Basically a search on Google will bring up a lot of scientific and observational info for you to fill in the blanks I might have left. I've recently fell in love with these fish and am excited to get my own after my baby platys grow up and they get moved to the big tank.