Need some help

This is my 120 stand, no support in middle like you are talking about.  I made a header that is two 2X6's with a 3/8" piece of plywood in between and fastened together with about 50 3" screws.  One year later and no issues, no sag whatsoever.  Also has some 1/8" plywood on the outside which is what you see in the pic.

 

i made a stand for my 125 out of 2x6's for the top and 2x4's for legs and bottom. just make sure when you do it that the load is not all on the screws. have the head sit on the legs and the legs sit on the base. it cost me about 40bucks worth of lumber to frame it.

 

I'm pretty sure the stand for my 135g has no middle support. I'd have to double check, but almost certain nothing in there and it was a DIY stand made from pine.

 

if you go on reefcentral there is a DIY forum, they have a good plan in there for stands. gives your cut lengths and everything, its what i used to make mine, works well. finishing it is the hard part

 

I've seen alot of people slide there sumps in from the end of the stand when they have to have a center brace. Or build it out of steel and you'll never have to worry about it! /DesktopModules/ActiveForums/themes/_default/emoticons/biggrin.gif

 

Should be just like figuring a span when building a house. If you want to span over say a sliding door you build a header. So I would say if you don't want to put in a center support double up on your horizontal support. But IMO that won't be needed, but if it were me I would do it anyway to be safe. The legs aren't a problem, if my memory is correct a 2x4 will hold 1900lbs. Snowman is right though, I wouldn't trust just screws.