my adult teardrop barbs actually started doing this also no sense moving it back they will just redig hole
I don't think this behavior is strictly mating related, I think it is partly just so the fish feel comfortable. In the wild, they need to watch out for predators, and what place better to hide than a hole you dug ? I find my fish often dig their "holes" in a corner or near/under wood and rocks, probably to hide from larger fish or air-breathing predators.I've kept an Oscar who did that all time. My niece has a Midas who does the same or worse.
I used to think it was strange since both were/are the only fish in the tank, but I guess it's just instinctive to do it in case a potential mate somehow appears.
I don't think this behavior is strictly mating related, I think it is partly just so the fish feel comfortable. In the wild, they need to watch out for predators, and what place better to hide than a hole you dug ? I find my fish often dig their "holes" in a corner or near/under wood and rocks, probably to hide from larger fish or air-breathing predators.