The quick answer to your question about using a 1 thick 4 by 8 sheet of Plexiglas (plastic) to hold back a 4 foot wall of aquarium water is NO!Ocean Railroader;4466142; said:How thick are the clear sheets that are holding back the water in the tank. In that I was able to run into a possible deal on a four foot wide eight foot long sheet of plexiglass aylic that is one inch thick. Would one inch thick plexiglass be able to hold back five feet of water?"