I had to cut my top off the durso pipe a little but was able the get the Maggie Muffler to fit, I also have screened tops on.
Or you can try something like this...
black kydex sheets, cuttable and heat moldable and from all the post I have read, plus my own experiences, it's reef safe. If placed over the top it blocks all light and will help reduce the growth of algae.
I just put gutter guard on the top of my overflows of my 125. I used little zip ties through the slits of the overflow to tie down the gutter guard and then put the other end of it under the rim of the tank. That way I can always flip up that edge to get into the overflow if I need to.
I chopped mine off for more surface skimming. I've read that's where the organics are. It lowered the water level in the display and I left the upper teeth for keeping fish out. Later on I cut them out completely.