I have a 20 year old Glass 125 (don't know manufacturer). This tank has developed a leaking bottom (bottom seam) ... 3rd time it happened. It is a "floating bottom in that the bottom outside edge sits inside the tank. In the past I've scaped the silicon out of the seam so the glass is flush ... I did NOT remove all the silicon joining the glass. I re-siliconed the joint and added pieces of glass and acrylic at the joints at various spots to provide extra bonding area. Now approximately 1/3 of each long joint (the 72 inch joints on the front and rear glass panals at the bottom) have this additional support.
The tank started leaking again after 3 months of use ... appears to be the middle of either the front or back seam ...
Ideas on better method? It could be an etreme amount of work to remove the glass/acrylic braces from the seam to remove all the existing silicon ...
Would a piece of 1/4 inch glass across the bottom (middle, connecting to the front and rear) provide any real additional structure?
Can I silicon over existing silicon?
you cannot silicone over silicone, it will not bond. if i understand you right the bottom is inside the 4 walls of the tank, as in the 4 sides are not sitting on the base plate. If that is the case just buy another sheet of glass measured to the total outside dimentions of the tank front to back and left to right, run a bead of silicone all round the edge, dot silicone blobs over the base every 3-4 inches apart and then sit the existing tank on the new base add some books, bags of sand or similar to inside the tank to help weigh the tank down and compress the silicone leave for two days and that should solve the problem......... assuming i understand what you described!!