I use poret foam as a tank divider in some of my breeding and grow out tanks. You can turn the divider into a filter. http://www.swisstropicals.com/Poret Filter Foam.html
I use poret foam as a tank divider in some of my breeding and grow out tanks. You can turn the divider into a filter. http://www.swisstropicals.com/Poret Filter Foam.html
I have used an old undergravel filter plate that I didn't need and cut it to size which worked quite well. To hide the ugliness, I just put some electrical tape on the outside of the tank and it looks pro. I have also used the plastic mesh that they use for cross stitching found in any arts and crafts store along with some of those old slide and grip report cover binding bars that slide onto the cover to hold the papers inside. Those report cover binding bars are kind of hard to find now a days (internet still has them but I cant find any at the stores around here) and are the same exact thing they sell for use inside those lee's tank dividers. Seriously though if I need something dependable and safe I just go to the pet store or online and buy the clear hard plastic plates with some of those suction cup fasteners. I can see the egg crate damaging fishes if they get aggressive.
I see where your coming from with fish hurting themselves. Do you think angels would get that agressive?
We use egg crate, but we took fishing line and sewed plastic window screening to both of the outsides of it. Keeps it permeable, but not fish penetrable. Works well for us in our breeder tanks.