I can't tell from the picture where this chip is located on the tank, relative to tank depth. I am also struggling to figure out the perspective in the first photo.
I would being that the chip is on the exterior, an epoxy repair would be sufficient. I would probably examine it closely with a magnifying lens to ensure there is no cracking that extends deeper than you can see. But otherwise, I believe an epoxy repair is sufficient and I do not see any added benefit from a glass patch on the outside.
What I cannot tell from that first picture though is what is the bubble looking thing below the chip? Its almost like the chip is much bigger if looked at face on but you did not provide that photo. If the chip is as bad as I think the first picture makes it look, then I would remove and replace the entire glass pane. If that is just some kind of optical distortion and the chip is as innocent as the second picture makes it look, I would just epoxy repair it.