GE Silicon I - White

[limmer]

I think RTV 100 series is supposed to good.
GE1200 series is good too.  It is called SCS1200 in the States.
I think you can get the GE here. 
This is what a lot of the tank building people use.
I use the Home Hardware brand also for small stuff.
The main difference between them is the strength.
This is what I found previously on the net.

SCS1200 Series

Hardness (Shore A)   28       
Tensile Strength     470 PSI   
Peel Strength      40 lb/inch   

RTV100 Series

Hardness (Shore A)   30       
Tensile Strength     400 PSI   
Peel Strength      40 lb/inch