This place is in Guangzhou, which is a 2-hour train distance from HK. It is by far the largest pet fish market I have visited in the south China region. HK fish street is another place and you can find around 100 fish stores all crammed on one street. The last time I went there I only saw what we local people call "blue patterned gar" which I think is Florida gar and "bliss gar" which is gator gar. Hope you have better luck when you go there.
Things are pretty well-regulated in HK, you'll not see drastic things such as a croc sitting in a tub on a crowded street. If you want surprises, I suggest you pay a visit to the Guangzhou pet fish market when you are here.