I think it is possible with casting epoxy resin. This resin does not adhere to clear pvc (office) tape. Place the tank on its side with the chip at the top.Than clean the glass put a piece of tape over the chip and a few drops of resin in it filling the gap.. Epoxy resin hardens within 24 hours, but than still is relatively soft. Thus if you spil a few drops over the glass, use a razor blade scraper and remove while its still flexible. Total curing time is 7 days, than it will be as hard as glass.Somewhere in between 24 hours and 7 days remove the tape.
Take casting resin, because coating resins oftenly has a yellow color, it can shrink while curing and it doesn't contain UV blocker, will turn more yellow over time. Casting resin usualy has UV blocker added and doesn't shrink and casting resin is crystal clear.
In the end you will always see a bit, more looking like dirt than a missing chip.
That's absolutely the best you can do. It's simmular to repairing a cars windshield chip/crack repair. A clear resin is pressed in almost 95% masking the repair.
Could be using the same resin as for car windshiel repair will do already.