I was doing wc last night and looking at my tank while thinking about your post. I may end up doing a combo sand and tile. I could place tile in center and fill in curves of over flow areas and other gaps with sand. The less sand, the better. I am having algae problem in my 125 & worry about picking up tile i.e. scratches or slipping! Funny, I don't have an algae problem in my 75 gal tank even though it also is close to a window. I'm hoping I'll have algae problem solved before I introduce my discus.
I love my cories. They work tirelessly and are so cute the way they hang out together. Here's what my sand looks like in the morning
Attachment 104839