Another thing you can do is swap the impeller out of your AC 20 and put it on your 50. Actually, the whole motor assembly can just be swapped. Then you get the flow of an AC20 with the capacity of an AC50.
Monday I expect the 206 for the big tank at home; Tuesday I'll swap in AC50 into the 10G work tank , and downgrade the motor from, the AC50 to the AC20.
side note: I've installed my second AC20 on my work 10G, to see how the angel handles it. She seems fine, but I run it off the same timer that does the light.
Also... an Angel in a 10g? :-/
I bought the angel at the local PetCo, for under $5, she was smaller then a dime at the time and white as snow. She spent the first few days hiding. I need/wanted a center piece for the tank. The dwarf puffer was too shy for that roll, and the Draft Albino Cory Cats, where not very exciting during the day time.
The angel is now about the size of a quarter, and orange. She follows me around the tank, and seem to enjoy the attention she gets (no longer hides). When she gets bigger I'll take her home to my 29G tank. (I'm thinking of evicting the current residence - that's another story.