Start here ... use at least 3.8 for a safety factor.
https://www.easycalculation.com/measurement/aquarium-glass-thickness-calculator.php
10mm glass is recommended for free standing...
not sure how they compensate for the required difference between side glass and bottom though..
bottom glass tends to need to be stronger (thicker) than side glass
The thickness of the bottom glass is covered by a set of specific calculations (thicker), but does not cover an aquarium which has a bottom glass that is well supported from below the aquarium in an even uniform manner. The surface 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. Significant time must be allowed for the filler to fully cure before the aquarium is filled. If the bottom glass is only to be supported by all four edges then use the special set of calculations. The same thickness glass can be used on a uniformly supported bottom as well and this will significantly improve the safety factor. If the aquarium is to be supported from below in a uniform distributed manor, then the same thickness glass that is used for the largest side panel may be used. To do so requires the supporting base to support part of the load so therefore it must be VERY strong."
Tempered glass can be downsized a bit..it's stronger How much???
Will completely shatter if damaged.
https://www.aquariacentral.com/foru...ottom-glass-and-frame-questions.203106/page-2
Also there is no drilling allowed since tempered glass is under both tension and compression.
Why it shatters into tiny cubes if "nicked"
Most relegate it to only bottom glass only. (ARGUABLE)
If the bottom gets nicked the water dump is catastrophic in nature unlike a simple crack..
Bracing can reduce the required thickness
Like a center brace makes your 48x30x20 tank to act more like 2 24x30x20 tanks YMMV.
Wouldn't include bottom unless equiv. braced..
Starfire is, so I've been told, slightly softer than reg. glass so for that and cost most would use it for viewing panes only..
Shows bottom thickness..
https://www.marineaquariumsa.com/general/glasscalculator.xls
10mm for sides 12mm for bottom..
high safety factor and based on "depth" of 508mm 20"
There are a lot of vids on assembly instructions and recommended silicone.
Floating the bottom is usually recommended.
