Personally I think plexi-glass (Acrylic) is better at distributing weight and also doesn't have the negative looks and other features of eggcrate! If you think about it, a solid, smooth surface is better at distributin weight, than an interlocking network of plastic plates with large areas missing. There is always the possibility (although minor) of sand becoming anaerobic within these open squares between the eggcrate. Also, eggcrate is hideous to look at in any kind of display tank!
1/4" of plexi is more than enough to keep the bottom (and any other sides) of the tank from having excessive pressure forming against small areas (pressure points). If you use it on the bottom of the tank (like I do), just add the plexi first, then add the sand. Make sure no sand gets between the plexi and the tank bottom, and you will never get any scratches on the protected area. Plexi is also more durable, yet pliable than glass, so it won't crack itself when heavy rocks are stacked on it. It will get scratched easy and get minor pits and dents in it, but WHO CARES!
I personally cut mine about 1/2" less than the overall inside dimensions of the surface I'm protecting, that way it fits snug without overlapping the silicone bead around the edges. You can then silicone it in place, if you like or not. I did not silicone mine and just laid the sand on top of it. I have had no problems at all, and I have large pieces of Limestone in my tank. Just for the record, I do have two rocks that are positioned more vertically than horizontally, and they lean against the rear glass, I am very careful not to push against these rocks when moving things around. If I decide to do anything to protect the rear glass, I will simply add a sheet of plexi (1/8" would probably do fine).
1/4" of plexi is more than enough to keep the bottom (and any other sides) of the tank from having excessive pressure forming against small areas (pressure points). If you use it on the bottom of the tank (like I do), just add the plexi first, then add the sand. Make sure no sand gets between the plexi and the tank bottom, and you will never get any scratches on the protected area. Plexi is also more durable, yet pliable than glass, so it won't crack itself when heavy rocks are stacked on it. It will get scratched easy and get minor pits and dents in it, but WHO CARES!
I personally cut mine about 1/2" less than the overall inside dimensions of the surface I'm protecting, that way it fits snug without overlapping the silicone bead around the edges. You can then silicone it in place, if you like or not. I did not silicone mine and just laid the sand on top of it. I have had no problems at all, and I have large pieces of Limestone in my tank. Just for the record, I do have two rocks that are positioned more vertically than horizontally, and they lean against the rear glass, I am very careful not to push against these rocks when moving things around. If I decide to do anything to protect the rear glass, I will simply add a sheet of plexi (1/8" would probably do fine).
