Then make the bottom square.

Then it is concluded that when the length and width of the box are both 20 cm, it is the largest.

So it is 20 centimeters long.

20 cm wide

5 cm deep

2.50× 20× 30 =30,000 cubic centimeters = 30 liters

So the volume of this fish tank is 30 liters.

[(50+ 1)×(20+ 1)-50×20]×(30+0.5)+50×20×0.5

=2 165.5+500

=2665.5 cubic centimeters

The volume of glass is 2665.5 cubic centimeters.