divider

I've seen references to "egg crate" sold at Home Depot, to set under the gravel as a scaffolding for rock piles and for use as a tank divider. Which section of the store would I find this stuff in? What's it's non fish use. (I'm not what you would call handy around the house.)

I am installing a 125 to serve as a divider in the living room. any ideas on what kind of filtration would be suitable without having unsightly wires/hoses, hob's. tank is not drilled. it will be for a group of fronts.