Sadly, the red zebra was deceased the next day. This is very unfortunate. Upon reflection, I'm reluctant to place any/all of the blame on con-specific aggression. Had it truly been stuck in the hole, it would have struggled to remove itself, which would have resulted in physical evidence on its body. There were no physical markings on it at all - no scratches, missing scales, etc. It was just pale and seemed weak.
I honestly do not know what happened to it. The fish appeared fine the night before and had shown no prior indication that anything was amiss. The fact that there were free swimming fry indicates that the egg laying and incubation period had long past, and I had not witnessed any parental aggression prior to discovering it lodged in the hole. If the fish was going to get beaten to death, in my opinion it certainly should have happened well before it did, not to mention that it should have shown some evidence of it.
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