Advice please?

[swampy1972]

I've got a pair that have spawned several times, but each time I'd expect to see wrigglers after a few days I just see empty egg casings.
I'm assuming they've eaten the young as they hatch.
The issue I have is the eggs don't seem to go through a noticeable colour change. They are laid dark orange and stay pretty much the same, although others go pale. Again, assuming these are infertile.

Since I've never seen wrigglers to confirm that they've actually hatched or were even fertile, my question is. Is it possible (or common) for the adults to eat part of the eggs leaving casings behind or are they eating newly hatched fry one by one?

Thanks. :?

[ILLUSN]

its normal to see bits of eggs left over once the parents eat them.

[swampy1972]

its normal to see bits of eggs left over once the parents eat them.

Thanks ILLUSN. By "bits" I imagine you mean only a small left over pieces. I have most of the case remaining. That's what makes me think they're picking off the young as they emerge.
Am I barking up the wrong tree or is this what you meant?

[ILLUSN]

its bits of egg shell next time they spawn cage the eggs or remove the female