When applying silicone on the glass, run a continuous 1/4" bead, with no gaps or bubbles.
For the best bonding results, apply only as much silicone as you can work with in 3 to 5 minutes, because after this the silicone tends to skin over and won't bond well to the glass.
Over the years we found that laying down a bead of silicone on the bottom glass for the rear and one side glass panel, and on one side edge of the back panel, installing the back glass panel on the bottom, then the side panel to the bottom and rear panel worked well to begin with.
When any section to be joined has been set into place, the silicone needs to be smoothed out. This is done by starting at one end of a joined section, pressing the tip of an index finger down into the silicone, then firmly and evenly, without lifting your finger, running it along the full length of the siliconed joint at a slight angle. Now secure the joined section into place with duct tape. There is no need to worry about wiping away any excess silicone that squeezes out from around your finger, as it can be cleaned up or trimmed off once the silicone has fully cured.
The supporting surface of the tank base must be very level. On very large aquariums this can be difficult to achieve, and self leveling filler may be needed between the polystyrene and the base. This should be applied just prior to fitting the aquarium to the base so that the aquarium’s weight levels out imperfections. Sufficient time must be allowed for the filler to level and fully cure before the aquarium is filled with water.