The skimmer is a coralife super skimmer 125 -- I think its still breaking in right now.
3/8" acrylic would work fine... I used weld on #4 and leak checked it. The sump had a small seep (I should've done the whole thing in the garage with more space but it was 15 below outside).
If you have a seep, what I did is take a small strip of acrylic and just weld on #4 it into the seam making it twice as leakproof there. You can hardly notice it (wouldn't with substrate) and I have two flourescent strips in the sump you can probably see in the pic. If you have more questions just ask
I have a feeling my frag tank is going to be more hands on than my display (more hands off and looking).