You can also use the pink stuff, but I really hated that for photography. It's just white styrofoam, something like 1/2 thick. It's just used to distribute weight incase there is a pressure point. People suggest using the pink stuff because it is "high density" and yes, the tank is used for more than just a hobby, but that's not what this thread is about.
Here are some specs:
4x4' acrylic tank with 1" sides and 3/8" bottom by ReefMania
Lights are 4x110w VHO actinics and 4x54 t5 whites off IC660
Return pump is a Sequence Dart - 3600gph
Skimmer is a ReefMania PS-8
Sump is a custom design using overflow style dividers also built by ReefMania.
In total there are 16 holes and 12 true unions.