I cull fish reguarly and not because of deformities either i grow out cichlid fry in ponds during the summer months.I always look for the smallest and weakest of the brood and the deformed but i have only had a few come september i cull them out and feed them back to their parents.I do this because i only want the better specimums in the trade and i figure that in the wild these weaker fish would be the first to be predatorised anyway.