A lot of large glass aquariums are assembled in home so that's not the hard part.
The resurfacing is a lot of work by hand. Now if you can talk a glass shop into leasing their tools/shop to you after hours, you might save a lot of time and still be cheaper than a new aquarium.
I went down this rabbit hole many years ago. What I gathered:
1. Silicone bonds to glass at a molecular level. Even when you have a seam separating, there is still a layer of silicone on both glass surfaces.
2. Silicone doesn't stick to itself (new silicone on previous silicone) as well as...
The best way for the animal is to take the chunk of rock out. Hopefully it's something you can chip off.
They are not like an aneome attachment. Anemones have be mobile slowly. The toadstool attachment is about as permanent as you can get without building a skeleton. Think of a mycelium...
I get some satisfaction from pointing at said coworker when people ask me what happened to the tank.
On the upside, I get a lot less visitors in the office now.
I HIGHLY recommend coating your container to make it water proof long term. While there are materials that are good for water tight containers, I don't trust petg long term. It's hydroscopic and layer adhesion will eventually fail.
If you continue with petg, over extrude and increase overlaps...
The tank is slowly recovering. A couple of coral I thought were gone had enough tissue survive that they are slowly growing back.
I'll take a full set of pics tomorrow when the lights aren't in evening blue.
I'm moving the clownfish and cardinal from my daughters biocube to my tank this...