I just set up my 210g. One overflow is running fine the other is just a small trickle compared to the other. One pipe is shorter than the other ciuld that be it????
I could get you pics but i dont know how to post them. They way its run is the left side overflow dumps striaght down into the sump, the right side comes down 3 inches to a 90 and then runs about 4 1/2 ft to a 90 to dump into the sump.
if ones higher it may just be a safety overflow, common in SW tanks here. Pretty much so if the main one clogs (common in SW) the other one kicks in to stop the tank flooding. if you want to use both just cut the pipe imo.