Duck Weed

[greenmumma141]

Looks like it.

 

[dave840f1]

I had a tank with Silver Dollars and smaller fish (Cardinals, Harlequins etc.) admittedly it was a large tank well planted but I had no problems.

 

[noobgamers]

apparently aeration helps stop it and goldies eat it maybe more movement on the top of your tank may help i reckon but only what i think would work