My tanks run very much on a system of 'survival of the fittest'. Weak and deformed fry tend to die off within weeks of hatching, being unable to compete against their stronger siblings. However, from time to time, I will have deformed fry (particularly in smaller spawns where there is less competition) that manage to survive to a size where I have to make the decision as to whether culling is necessary.
Zig-Zag (pictured above) is the result of a breeding between one of my Betta brownorum F1 males, and the F0 female. The spawn took place just after I'd finished up a copper based treatment. In fact, there was still copper in the water when the eggs hatched, and so I wonder if this had an adverse effect on the skeletal development of the fry.
When he was younger, Zig-Zag's spine was so severely bent it looked like a concertina fold. It's actually a miracle his digestive system even functioned as it should. Out of that same spawn, there were only two other survivors. One fry that was perfectly healthy, and one fry that was completely lacking its caudal, dorsal, and anal fins.
However, while I culled the second fry, I couldn't bring myself to cull Zig-Zag. I personally hate killing fish, and I simply couldn't kill Zig-Zag when he was not just surviving, but absolutely thriving. His disability didn't hinder him at all. In fact he's always matched his healthy sibling in both growth and aggression (a trait this line seems to have in spades).
Weeks later, I am glad I made that decision. Nowadays, apart from a shallow indentation in front of his dorsal, Zig-Zag's topline is almost completely normal. Obviously, he will never be used in my breeding program. But he will definitely spend the rest of his life here with me as a treasured pet.
With that said, I am hoping his remaining sibling is female, as I would very much like to cross her back to one of my two F1 males and see what they produce together.
Hailing from Melbourne, Australia, I currently keep and breed a number of species from the coccina complex.