[Zapins]

I have an old tank that has very dirty glass. The calcium buildup is not responding to vinegar soaks. Are there any other methods of getting the calcium out of the glass without killing any future fish/plants?

Possibly some chemical like CLR

 

[Zapins]

It isn't a crust of calcium, it seems like it has seeped into the glass.

 

[Zapins]

Is the grit safe for the fish? And is the etchin on the surface or further down? I can get a random orbital sander for 30$ and some 27000 grit. Will that work?

 

[Zapins]

Hmm, the tank is empty and has been for months. The soap will be ok? Won't the metal scratch the glass? My razorblade has scratched the glass before when I used to scrape GSP off.

 

[Zapins]

Woah... that is some strong stuff!

I'll have to try that then.