I think it is AWESOME! And I lovedddd reading your post!
How thick are the pieces? Because they look fairly thick, which would mean that it might be heavy.
If the pieces are thick, then the only thing I'd mention is - you might want to glue slate on the bottom too as a counterweight for the back for anytime that the tank is empty, because right now it would be more likely to flip over and then crack.
Especially true for the 60 ... that is a LOT of weight hanging on the back wall without a counterweight it might destabilize the tank itself. Also with that much weight on one wall, I'd make sure to constantly check the sides and bottom for leaks so I could catch them early if they happen.
But I think it looks AMAZING!