Other than the Y pipe up front all the tubing is flat, just looks like that in the pics. I usually run the nano in my 14 and watched to make sure the returns were getting flow and they are. It tends to keep food circulating better with it on than off. Some food will still get by but overall I just leave it on when feeding in the day and turn it off at night for the acan, dendro and candy cane feeding. Then I have to worry about the cleaner shrimp stealing their food! I saw, I think, Justin running his nano in that position in his 8g and thought it would block the returns too till I tried it.