Duckweed
 

I have a 55 gallon tank and I'm running not a really fast current filter but fast enough that the duckweed never can settle. The filter is a hang on that is right in the middle of the tank and there is no where else i can move it, so i put up two pvc pipes to push the current down and keep the duckweed in the same place with a still surface. This worked well for a couple of days until recently the pvc pipes have been falling into the water releasing all the duckweed and i have to set them up and start all over again. Any ideas on how to keep the duckweed and not change my filter?

As long as there is surface movement the duckweed will never grow to its full potential which can be a blessing as it can go crazy, I'm afraid the best option is a filter change. An idea I don't know if it will work but would be to grow the duckweed out in some other medium until you have enough to cover the tank so even if with the surface movement the duckweed has nowhere to go.