[kekon]

I also used urea. Moreover, i dosed 3 forms at the same time (NO3, CO(NH2)2 and NH4). I also noticed bigger leaves grow on some plants. The point is (but i'm not 100% sure yet) that by dosing urea and NH4 one can keep lower NO3 levels but maintaining the same growth which is achieved by dosing only NO3 but in higher levels. I didn't notice issues with any type of algae. I was encouraged by "Drak" firm which produces N fertilizer for planted tank which includes 3 forms of nitrogen. The daily dose is 1 ppm NO3, 0.1 ppm NH4 and 0.33 ppm urea.

 

[kekon]

I still have the Ludwigia Glandulosa which sometimes grows fine and other times doesn't.

I saw similar effects and it seems better growth occurs when NO3 is lower.
Blyxa Japonica is a plantwhich really appreciates high NO3 levels; i've never had any issues with this plant. I grows like a weed at NO3 10 ppm or more but some plants are severely stunted.
I'm still waiting for my ordered circulation pump but i think it will not help much.
I noticed that NH4 and urea work better in very soft water. In harder water NO3 is better. Generally speaking it seems that the harder the water the more NO3 can be dosed without harming the plants.