DuckWeed out of nowhere!!!

Last week when I uncovered the tank I got a SHOCK! 8-()
The surface was covered totally with Duckweed!!! I wondered why the tank looked like a Low-light set-up (for a minute I thought some of the lamps where dead)
This weed developed after just one week. Not that long ago I added one Lotus Zenkeri and probably one tiny Duckweed slipped into the tank. Enough to take over the whole aquarium!
I took a fish net and removed all the Duckweed. There is probably some left.

These days it looks like this

I am very happy with how this scape looks today. Not too wild but still jungle looking.
I perform 50% water change every week and clean the external TetraTec EX 700 filter every month.
I dose Tropica PlantNutrition+NPK 3x a week (15ml each time) I also dose some extra KH2PO4 once a week since Tropicas fertiliser doesn't contain enough of P in my opinion (see Tropicas declaration on www.tropica.com ).
I dose GH-Booster (Noraq GH-Salt) for extra Mg and Ca every week after the wc.
Also after the wc I redose with Bicarbonates (1 teaspoon not much)

Big Time for Update!

This tank has changed it self :-) I didn't have much time to maintain it and this is what happens!
The Pogostemon helferi pushed out the HC (grew over it + some HC which became too tick floated up).
Photo taken after I removed the P. helferi mountain ;-);

Later on I took the Hygro Rosanervig out and planted Hygro difformis instead. I also added a few stems of Alternanthera reinecki (red plant). Acicularis grass and P.helferi became the main foreground plants, accompanied with some Blyxa japonica and a strange carnivorous plant Utricularia sp.