Would you use this DIY tank?

[FranklinDattein]

Remove that epoxy and stick another layer of glass on top of the junction. Use plenty of silicone. I have had a tank with cracked bottom, patched like this and it will last forever.

I would also worry about mineral deposits on the glass. Depending on the degree, it is impossible to remove, unless you polish the glass (which is probably more expensive than a new tank). Given by the amount of coralline, I guess there will be mineral deposits, as well.
Top it up with freshwater and check if the glass stays transparent, without white stains.

 

[Ace25]

Remove that epoxy and stick another layer of glass on top of the junction. Use plenty of silicone. I have had a tank with cracked bottom, patched like this and it will last forever.

I would also worry about mineral deposits on the glass. Depending on the degree, it is impossible to remove, unless you polish the glass (which is probably more expensive than a new tank). Given by the amount of coralline, I guess there will be mineral deposits, as well.
Top it up with freshwater and check if the glass stays transparent, without white stains.

There are plenty of etches in the glass from the coralline after I scraped it off. Done this a few times so I am familiar with the issue and learned how to fix it. I use a $20 bottle of Liquid Diamond glass polish with a high speed buffer and a couple hours of work and it gets it almost as good as new again. Tried many other solutions I read around the web, none of them worked nearly as well or quickly as the method I use now. It won't remove deep scratches, but it will fix the etching issue from coralline.