"Dave" wrote in message
news:5gtyc.307$n35.99@newsfe2-win...

Most DIY sites show that the side panels should be resting on the
bottom panel. All manufactured glass tanks I've seen are built
this
way. The forces on the bottom joint are mainly shear (water
pressure
pushing the side panel out), with some compression from the
weight of
the vertical panes. When you only support the 4 corners, you are
asking the silicone to hold the bottom pane up to the vertical
panes,
which places the joint in both tension and shear, and silicone is
stronger under shear than tension IIRC. While it may hold for
years,
you may be stressing the silicone to the breaking point. I have
this
mental picture of very small earthquake, or just a 2 pound rock
slipping from your hand a few inches above the substrate being
the
proverbial last straw. causing the joint to fail all at once,
opening
up like a zipper, causing the bottom pane to break into many
pieces.

Now that would be cool to watch. Cleaning your 55g fish tank and
dropping a small rock or something and "whosh", the whole tank falls
into the base. Ever happen to anyone? I'd be LMAO for a year or so.
Sounds like a good stunt for one of those TV shows. Fish maintanice guy
shows up and starts to work, and "whosh"! LOL