Another possibility we've been overlooking...
Fish, when bred in a location other than the one to which they are native, are often referred to by the breeding location. Example: German Blue Rams! Native to: South America... Bred in: Germany.
I believe I have heard of the Taiwanese Pleco. Though these are clearly not an endemic species (clearly!), some Taiwanese breeders may have had success with breeding the species, and may be able to sell them quite cheaply.
Why are they clearly not endemic to Taiwan??? I can certainly explain this in a couple of paragraphs, if you're interested...
Plecos are part of a family of South American fish called "Loricariidae". I work for a Loricariid ichthyologist part-time, so I can tell you 100% that these guys are native only to South America. They're also all tropicals, or sub-tropicals, so they like warm water.
Why couldn't they also be found in Taiwan? Because they are not found in Africa, Australia, Antarctica or India. These continents (which when they were connected many millions of years ago were called Gondwanaland) broke up well after Asia and North America broke away from Pangea 180 Million Years Ago. If we don't see Loricariid fish (or fossils of them) in Africa, India, Australia or Antarctica, the family of fish must have evolved after the split of Gondwanaland about 180 MYA. Therefore, they certainly couldn't be in Taiwan.
There's more fiddling with continent arrangement that could be done... but there's no doubt in my mind that Loricariids are not found in Taiwan.
That is... if you believe in evolution
My ex-girlfriend is Taiwanese, and could probably help out if you need her to translate a link written in Chinese or Taiwanese. Let me know.