no.. they are good at controlling FA (fillamentous algae) and other water plants in ponds, but they can't really "filter" it out of green water.. well.. fry will eat algae.. but not bigger fish..
cover so that the tanks are not in direct sunlight.. after the initial algae bloom, you can usually uncover the tanks.. something in the dying algae inhibits a second bloom.. but if your water has too many nutrients (underfiltered or overfed) you can still end up getting a second or third algae bloom.. if thats the case, keep the tanks covered, and get more growbeds online.. oh.. and during the bloom, it's a good idea to add aeration (personally, i think aeration should be added anyways)