I can't seem to get a straight answer. It seems like the community is divided on this.
Is there any negative effects on the offspring when breeding two homozygous dragons together. Say hypo x hypo. Zero x zero, trans x trans. Breeders I know swear by only breeding het x het. But I've also heard that this superstition is debunked.
There is no issue with visxvis in older well established morphs because the bloodlines are diverse enough to have been strengthened after all the selective breeding was done.
However in newer morphs like zeros and witblits, it's generally frowned upon as the genetic diversity isnt the yet. Breeding visxhet introduces new blood to the line to help diversify and strengthen it. Most breeders realize this and are responsible in that aspect.
In other words - the newer morphs bloodlines still aren't diverse enough to support visxvis pairings so visxhet is used to add new blood.
I know of a breeder that does visxvis zeros and just looking at pictures you can tell they look almost sickly.
A lot of breeders do use hetxhet pairings for the dragons they are producing to sale because that leads to predictable outcomes.
However, that is not what is used generally to produce new morphs and patterns and colorings....