I came across an article that explains how to calculate the lights needed for a given surface area. In my case 1 metre lenght and .4 metre width gives an area of .4. Metre squared.
Now we multiply the area * 33000 lux (medium to high tech is equal to 33000lux) which gives an answer of 13200 lumens.
There was also a chart that states that a t5 tube is equal to 70 lumens per watt plus another 20 percent if there is a reflector which gives 84 lumens per watt.
Finally we divide the required 13200 lumens by 84 which equals to 157 watts.
So 4 * 45 t5 tubes in a 200 litre tank , is enough light intensity for the majority of the plants. (if the tank is more then 60cms high , you have to add another variable.)
I do not know how to translate this to led bulbs, lumens per watt ,
And that light is emitted in one direction.
So any help / correction is greatly appreciated.