I agree with plantbrain.
I think the glass you selected will not strong enough for the tank. The problem here is the lack of a brace. I think you can build the tank, but you will need the braces.
As much as I hate being the engineer, let me demonstrate.
In a stationary fluid, the pressure is P=rho*g*h, where rho is the density of the fluid, g is Newton's gravitational constant, and h is the depth from the surface.
If you really want to be correct, we should also add on one atmosphere's worth of pressure due to all the air on top of the water pressing down on it.
The reason that's not important usually is that the same air pressure pushes on the side of the aquarium walls and the net force is just from the water.
Still with me ? Good !
I'll do this in SI units and convert it in the end for you. The density of water rho is 1000 kg per cubic meter. g is 9.81 m/s**2, and h is any number from zero to 22 inches, the height of your tank which is also 0.5588 meter, depending on how far down the side we are.
The width (W) is 48" or 1.2192 meter (I am not bothering with the thickness of the glass for this case), and the total height H of 22" is 0.5588 meter.
Hold on. Almost there !
The force on the front side of the aquarium is the area of the piece times the pressure where the specific piece is height wise.
We'll think of little strips of height dh, width W, and depth h. The area of each strip is W*dh, and so the force on the strip is rho*g*h*W*dh.
For example, a 1" front panel strip at the bottom of the 22" high tank would have a pressure force of 169.759 Newtons or approx 38.17 pounds.
If we add all these up, we integrate over h, and get 0.5*rho*g*H*H*W.
Putting in the numbers, that's about 1867.354 newton = 419.7978806 pound-force
A total of 420 pound force pressing on the front panel.
To better visualize this, imagine the front glass pane supported only on the ends with two saw horses, and a 420 pound man standing on top in the middle of the pane. Do you think your glass thickness will take that ?
The sides will obviously be less, but the front and back panels will take the brunt of it.
Your glass thickness is insufficient, and the lack of braces just further condemns this project.
Nick