Thanks Mariannep & Michael for your input
There is an English link to that Spanish write up, so no worries and I done a quick reading on it. It's amazing there isn't any algae bloom with a tank with direct hit with sunlight (advantage of heavy plant load).
In tropical climate countries like Singapore or Malaysia, the most common issue I would encounter is algae bloom and turning the water green very quickly once we have a tank exposed to the sun every day. The only good thing about this is, if you are into cultivating daphnia for your fries, the daphnia will have a feast! HaHa
The current water parameter for this nano tank are approx:
ph 7.5 (I don't use a pH pen, yet)
ammonia & nitrate is very little, 0.5 ppm or less
nitrite is at a level of 20 ppm, it's at the peak perhaps now
One plant that I thought would be easy to survive was elodea densa or anacharis but to my surprise, it melted in 2-3 days. Which makes me think, this plant do need a fair amount of light. It is so commonly available in the lfs, I am curious how they cultivate this plant, need to ask more....
I have a long long list of so called low light plants but currently am trying out the plants you see in the photo. I am not that confident that hairgrass will multiply and carpeted the tank, but we shall see.
Btw, I did add some mineral ferts (from ADA, very expensive) at the bottom of the tank before I add 1 inch of normal potting soil. And after that, I added some broken coral chips, and 3 Sera's fert tablets before adding another inch of gravel.
Since it's a nano tank, I don't think it's wise to over plant it, so, I am hoping the hairgrass will grow more and the tank will complete it's cycle before I start a new tank, with some other plants. Btw, I have 2 nice bettas that I am keen to transfer to such tank, so that I will reduce the frequency of water change.