To draddttg: Actually, I have started with a 2 ft, complete with overflow and sump in 2001.
Then, I got a 4ft IOS in early 2003, which is wrong for a marine set-up. It is now a chiclid tank.
The thing with my present 5 ft is that it is built to fit into a hole ( which was hacked for this purpose) between my bedroom and my living room, so that the aquariunm can be viewed on both sides.
This leakage is really a heartache for me. Actually, after hearing so many suggestions, im at loss at the solutions.
To silicon only?
Or to just make another main tank?
Or to do the whole set-up again? $$$$$