glass thickness

How tall are you planning to build the tank? That is a really big piece for fairly thin glass, even tempered.

I saw that, however the bottom thickness is important too. The taller the tank, the more pressure there will be on the bottom seam.

So it kind of depends on how you plan to build the tank, will the sides be around the bottom or on top of it? If they are going around it I'd go with a thicker piece of glass or do a brace around the bottom on the inside. The reason is because the thicker the glass the more silicone you can use which will hold better. This is the reason you will often see a thicker bottom panel than the others.

If you are going rimless on the bottom and going to fully support it you *should* be fine. If you are floating it I'd be a bit more hesitant.

http://glasstalks.com/2011/03/16/physicalproperties/

The compressive strength of glass is 12x it's tensile strength, so if the bottom is fully supported such that it can't deflect, I'd think it'd be fine. The concern for the bottom (to me) is that thin glass can be damaged by impacts (even if it was set perfectly flat), but that's why tempered is valuable in that situation. Uniform, fully supported pressure with minimal sharp impacts should be fine.

I'd try to make sure large sharp rocks aren't in the tank such that they can fall and hit the bottom. You still may have to be careful to avoid stress fractures while moving it or building with it, or it least it seems that way to me. I see a lot of posts by people who cracked glass in movement, not in actual use, although that's anecdotal at best.