160L = 160,000cm^3
Not too sure about this one....but I believe that an edge of ∛160,000 ≈ 54.288 cm in each dimension will minimize the cost......total area of the glass = 5 * (∛160,000)^2 ≈ 14,736.126 cm^2
[ You forgot to convert liters to cm^3......your configuraion uses 4000 + 3200 + 8000 = 15.200cm^2 of glass ]
This lessens the required glass in your configuration by about 464cm^2
However....aquariums are not usually designed as cubes... [ maybe because of too much water pressure on the sides?? ]
Maybe two of our other members - Alan or Heureka - know of the most efficient [workable] design......???