Shallow is correct, even with the biggest numbers I have heard, after a few generations, it would be almost impossible for cousins not to be being breed to each other outside of Austrailia. Even getting them from many locations in the US or Europe, they would have to be related, unless someone has smuggled out more.
I think what your trying to say, or I am hearing is that as more generations share the same ancestry without any trace of unrelated blood, more problems are surfacing. When that is combined with breeding daughter to father or siblings to get the screaming colors, its a potential for disaster I have one GG female that is a Europe/US cross, another that is a male GG breed by closely traced lines going back several generation. Both are wonderfully heathly and never had a problem, 600+ grams and stocky and longer than average, gold colors, and seem far more intelligent than the beautiful red sandfire I have or the other 8 normals/high colors.
The Sandfire has a host of problems, is small but eats well and has a problem processing calcium. He does not have MBD, we've had him x-rayed and blood panels, but the calcium settles in the joints of his hands, similar to gout, but with calcium instead of Uric acids. Our Vets thinks it is caused by inbreeding. Of the ones I have, all from different locations and breeders, only two females would I even think about breeding and only with one of the males we have.... the others are and will be pampered pets, as their genes should not continue, they are not my idea of strong, healthy lines and even though beautiful and would produce colorful babies, its not worth it to me or them.
Too many people are breeding just because they have a male and female, with no background history or concern for the future health of the offspring, I commend breeders that are closely watching those lines and trying to diversify as much as possible. I also think with the proven history of health of the GG line, crossing this into normals is a good move, but what do we do when that one too is exhausted?