I have duckweed in my planted tank... I acctually like it there-- I just clear out about 50% of it every couple of weaks to keep it under control.
if you wanted to totally get rid of it.. just take a net and skim the top of the water untill its all gone-- its invasive but the good thing is that 99% of it stays on top of the water so its not that hard to catch
if you wanted to totally get rid of it.. just take a net and skim the top of the water untill its all gone-- its invasive but the good thing is that 99% of it stays on top of the water so its not that hard to catch