This might sound "out-there" but compared to $4500 for the TV star to clean up the tank I think this might map a little more sense.
You could remove the glass, return and overflow. Then install/build a new glass tank inside the frame, which would eliminate contact with all of the Metal. The bottom glass could be drilled for return/out flow access. You could use clear acrylic tubes attached to bulkhead fittings for your return/outflow plumbing.
A canister underneath could be house in an antique box or chest.
The substrate lights could still be used as they would be able to shine through the glass base. Maybe use LEDs in those fixtures.
Above hand a PAR38LED, the bulbs kinda steam punk to begin with.
Only down side is you loose the cool fountain outflow & return.