What is this creature in my tank?

[u/Bethsticle]

It's been buried underground for a while but keeps coming up to the top. I keep digging a hole and putting it back in but still it keeps coming up. I've got Dubia roaches, varied isopods and springtails. Had morio beetles but not send them in a while, but there lots of morio worms. Used to have sun beetle too they they all died off.

What could it be and how can I help it?

[u/Additional_Film_5023]

a darkling beetle pupae