Standard overflow in 90, questions


Reefing newb
I've had my tank for about 3 years now. Its had its ups and downs. Some short learning curves and some LONG ones. This is one of those. I got my tank already drilled and mostly assembled. The Durso overflow and box were already in place when I got it. My big question is..... can this box section be removed without draining the tank? I'd like to leave the overflow in place as well as the return line while I clean the cover. Can this be done?

Reason you ask? Well, it really needs to be cleaned up back there. Lots of unwanted algae and I have Copper Penny Palyos taking over my tank! The front of the drain cover is, well, covered with them. I'm planning on getting some new dry rock and slowly swapping it out for the stuff currently covered with these palyos. I'd keep them, but they have no color. They take over and choke out Zoas and mushrooms. I know that I'll never fully get rid of them but I'd like to decrease their numbers significantly!