I called Mason glass who sold me the new bottom, although not aquarium builders they know the nature of glass framing and removal. Basically they confirmed my worst fears and told me that when glass is framed between glass with no relief like in a custom skylight where glass is large and thick and grouting or silicone is minimal between the glass, not to remove any more of the proactive grout as the glass will expand and shift possibly impacting the other nearby panels sharing off chucks of edge glass. The way they do it is by removing any manageable broken pieces first then scoring small manageable sections and further cracking the glass from the back side of the score. Trying to remove too thin a grout on large thick glass will only shard the edges of both pieces of glass.
So it looks like I need to buy a glass scoring tool to get this thing out safely:nilly::thud::duh::irked::crazy::wall:
So it looks like I need to buy a glass scoring tool to get this thing out safely:nilly::thud::duh::irked::crazy::wall: