Duckweed not growing!

8 gallon bare bottom tank.
Inmates - 2 females, 1 male - guppies and 7 fries.
Plants - Elodea Najas floating plant and duckweed.
Filters - 1 small sponge filter.
Lights - None

I have duckweed kept in a small pot near a window and it grows fine.

In the tank, I have added a ring at the top of filter to minimize propagation of bubbles as I thought that as the reason for duckweed not growing in it. The duckweed gets to the corner of tank and gradually dies. The tank is not placed so close to the window. Is less growth due to the lack of light ?

 

I think lack of light and lots of other floating plants may be the issue. Maybe get a light or move the tank closer to a window?

 

8 gallon bare bottom tank.
Inmates - 2 females, 1 male - guppies and 7 fries.
Plants - Elodea Najas floating plant and duckweed.
Filters - 1 small sponge filter.
Lights - None

I have duckweed kept in a small pot near a window and it grows fine.

In the tank, I have added a ring at the top of filter to minimize propagation of bubbles as I thought that as the reason for duckweed not growing in it. The duckweed gets to the corner of tank and gradually dies. The tank is not placed so close to the window. Is less growth due to the lack of light ?

Yes. It seems you may want to get a light. Duckweed likes very little agitation also.

 

There is not much floating plants. Only one more - Elodea. I can't move it close to the window. May be I will get a light. Any other suggestions are welcome

 

Get a light first. Could be agitation also but I have duckweed and its gets tossed around from two filters and its growing decent. Could also be lack of nutrients. Elodea is a nutrient hog. Could also be chemicals secreted by other plants in your tank which may be inhibiting duckweed (probably doubt this is the problem).