I have seen people rehome their fish on Craiglist before. (the link to craigslist New Zealand http://geo.craigslist.org/iso/nz
) Although the site I use is for the Washington DC metro area which gets lots of activity. It doesn't look like there is too much activity on the NZ pets section.
I thought of Craig List. But they are very quiet on pets. And the same with Trade me.
There is the Aquarium Forum New Zealand site ( http://www.fnzas.org.nz/fishroom/
). They have a private exchange/trade section. Maybe someone would be willing to trade you for your pesky little guys.
Yes I am a member of that forum. The only trouble is shipping of these fish. No one in NZ really ships the fish. And if you do ship the fish the price is very dear. Plus as far as I know they only cost $2.00 per fish and the shipping would be over $50. And at that you are lucky.
Who knows, there may be someone on this forum from NZ besides you that wouldn't mind taking them off your hands.
I will have another sniff. But I know one thing not many NZ fish keeps are overly exotic. They just stick to the normal fish. And Loaches are to most people a boring fish, they like Corys here. Although their are quite a few like me with Loaches, just not that many.
Hope this helps,
Cheers, and thank you.