I've seen some hydroids in the past that resembled this. But they were smaller and in dark spaces on my rock. Not quite the same I don't recall the ones I saw being exactly geometric.
I can't tell what that is growing on. But since it's my tank I will be prepared to hear it's a nuclear devils hydroid.
I can't tell what that is growing on. But since it's my tank I will be prepared to hear it's a nuclear devils hydroid.