Hello; I have a survivor in my basement. I have had it since the early 70's.
I have been able to seal it with silicone and had the seal last a while. It does take some care to trim the old tar back as much as possible. The post stating that silicone does not adhear well to slate may help explain why the reseal jobs did not last as well as the all glass tanks.
The last issue was with the slate becoming porous enough for water to seep thru slightly over time. Perhaps some one will have a suggestion for a coating that will paint onto the slate and silicone will adhear to. At any rate I have been able to get it sealed and the seal lasted for a few years on a few occasions.
The main issue will be an increased chance of shock hazard. I had the metal framed tanks and the stainless hoods on a metal stand. I have been bitten by stray current on these setups a number of times. It can be dealt with, but a person need to be more diligent that with the newer all glass tanks and plastic hoods.
I like the way they look and the corners are well protected so they do not chip. They are so much less prone to damage when being moved.
Good find and if the glass is not scratched up you can have a sharp setup.
