duckweed not growing to maturity
i have been developing a duckweed aquaculture project in my greenhouse for 8 months coupled with feeding that plant to Tilapia fish. we grew duckweed all winter with excellent results and fed all the plants to our ducks and chickens. then 3 months ago we bought and stocked Tilapia in 100 gallon tanks but as they became 'needy' of the food the duckweed just stopped maturing. i makes millions of what we call babies but doesn't develop the mature leaves it used to. the pH and temperature is fine and since we monitor the Nitrogen levels for our fish find that the duckweed ponds are rich in nutrients. we have not harvested the young plants now for two weeds having been recommended that perhaps they needed to be more dense and that the young are not nutritious enough for the fish. we have millions of babies in our multiple tanks and have even removed 50% to lower the density and also left other tanks to just fill up with the babies thinking that they needed to be piled on each other. any ideas.