May have been luck, or possibly yours (as fry) weren't separated from the parents and so learned the behavior. I've read that stripping mouthbrooders results in the fry taking longer to learn the necessary behavior when they mature and spawn. That's why I'm leaving the fry with the parents unless they suddenly start disappearing.
My pair were excellent parents from the first spawn as far as tending the eggs and wigglers, but then the fry would disappear within about 24 hours, within a week of becoming free-swimming if I remember correctly. That happened through 5 or 6 spawns, then I moved the parents to another tank to allow the fry to grow out and the BN to breed. It seems the adults were also eating the BN fry as they came along, though they missed one that was close to 1" when I found it.
I also discovered 6 larger oblongum fry among the plants, 3 each from 2 previous spawns. After I moved the pair to another tank the ramshorn population went ballistic. Up until then there were only a few adults to be found, and no smaller ones at all. The oblongums eat them like candy.
