[Reefmaster]

steve what you are looking at isn't really a big deal for the stand. depending on the age of the building might be worth beefing up the floor joist but i could guess better with age of building, storey you're on, floor type etc.

as for the stand i built, as bruce indicated i went with a notched post/beam frame with 3/4" plywood glued/screwed to that. either one of these structural elements should be able to support the weight of our 135, but i wanted redundancy in the event one should fail for whatever reason. so i have 2x4 verts notched with 2x6 horizontals, for the front and rear, and then notched 2x4 verts and horizontals on each end.

bruce yup i span the entire 6'. the doors open to give me more than 4' of access with no centre posts. its a nice feature.

i wouldn't suggest using steel. the thing about steel is it is a great tensile member (it is very strong if you pull on the ends of it, but not so great if you support two ends and load the middle). of course you could go with an i-beam or box beam etc, but why bother. wood is strong enough, especially since most of the load from our tanks come down on the four corners, so a good piece of plywood across the top and you're laughing.
anyway just my thoughts. shane