There have been a few reports of breeding BGKs from Australia. IIRC it was done with some pretty large tanks. Basically it is no easy task. Can't find the article on it now, anyone else have it?
I don't know where the article is but I've heard the same as andywg, large tanks are definately required and I don't believe sexing them is very easy so you may not even know if you have a pair.
I know blueice is very knowledgable in BGK - PM her, she may know the answer.
My friend has an ENF - quite nice fish by all accounts - will need a big tank, similar growth to the BGK apparently (BGK up to 22")