Duckweed Problem

[PrairieSunflower]

I am trying to grow duckweed, mostly in my betta's tank but I have since moved a tiny bit into my larger tank as well.  I seem to be having trouble growing it... and I know it is supposed to be that plant that is near indestructible!
 
In my betta's tank I have several anubias nanas, moss balls and amazon swords, all of which are doing well and have good color.
 
I used to use a fertilizer from Maidenhead aquatics and decided about 2 or 3 weeks ago to switch to using Seachem Flourish (http://www.aquaessentials.co.uk/seachem-flourish-500ml-p-300.html).%C2 I added the duckweed at about the same time I started using the Seachem Flourish.
 
Anyhow... they seem to be not as green as they should be and fading somewhat.  I was reading and it said it could be either a lack of fertilizer or too much water current.  I *think* Seachem Flourish is enough, right?  It is doing fine with my other plants... so, could it be the current somehow?  I have a hob filter with a directional spot that I point at my heater to break the flow for my betta, but the duckweed does continuously swirl on the top.

Or... I was thinking if it is the current... could I use air hose and corral the duckweed a bit into an area and thus be blocking the current?

 

[DrRob]

Faded and poor performing duckweed screams of lack of macro nutrients. They get a lot more light and CO2 than anything else so are very good at growing in well stocked (occasionally overstocked) community tanks where the fish provide the macros. Flourish does contain some macros, but very little.

 

[BerryAttack]

i have water lettuce in my tank and find that they just like to sit on top and not move. but if they do its at a grandma pace. 

 

[PrairieSunflower]

Maybe that is it.  The last time I had duckweed before this was when I didn't fertilize at all and had guppies.
 
Is there something else I should be adding to my tank so that my duckweed takes off?  I will see if I can figure out another placement for my filter so that both my betta and the duckweed are happy with the current.

 

[PrairieSunflower]

UPDATE:  After my last post I changed the flow the little bit I could and it has done the trick.  The duckweed swirls a lot slower at the top and has begun to multiply.
 
New question... once I have a much better coverage of duckweed, can I change the flow back to the way it was without them dieing off?  I read something online about the flow being too fast so they can't multiply with each other... but once there is a significant number surely current won't be a problem since they'd be all touching at that point... does it work that way?
 
Also need to look into getting a feeding ring shortly so I can keep a space free from duckweed.

 

[DrRob]

Yes, it works that way, unless the flow is insane.