Hi,
A more real issue that you may have is that the smaller pleco's are actually not very aggressive feeders.
From what I know of Africans, and I am by no means an expert in that area, is that they tend to be fairly aggressive feeders, so by the time you pour enough food in there for your expensive pleco to get a feed, your fish keeping experience will become quite different.
So even if you find a pleco that can live in the water, and if you can find one in NZ, then the next question becomes, can it be kept alive?
Just another thought.
Go on get another tank. You know you want to :happy2:
Cheers.