Hello there everyone. I bought a huge acyclic tank a few years a go and I'm ready to fix it and start building a new reef. In the back of the tank there are two slits that fall into an outside overflow box on both sides of the tank. One of the overflow boxes are missing. I would like to patch these slits and put a glass holes overflow in the middle. I have this overflow on my tank now and really like it. Next i want to patch the return holes and put my own in because the holes are way to small for reef flow. After that it needs to be sanded to remove scratches. After all that i would be good to go. My questions are how should i patch theses slits and holes and whats the best way to go about sanding. The pictures are below thanks again.
