Rooftop coco peat garden


I am new to hydroponics and farming world and it’s just few months and I am finding a bright future in hydroponics.

As I am new to this farming business I am planing to start a rooftop garden with coco peat. This is just to get basic understanding of different plants and there requirement.

Before I start this I did some paper work and found something is wrong on what I have researched or learn from reading blogs around the web. Please correct or guid me if any thing is wrong according to my understanding.

[li]First I am going to build a polyhouse on roof top to grow around 25 different types of veggies and fruits in area of 600 sq ft.
Approx around 70 to 80 plants I will try to grow in a growing bag.
Each bag will have 5 kg of coco peat.
[]So this is just a calculation done by myself
Each growing bag will need around 2 liter of water every week.
80 Plants * 2 Liters per week
Which is equal to 1920 Liter of water for 12 week. Which is quite a lot I think. 

Am I doing anything wrong in calculation ? Please correct me with this.