If you desk can't hold the tank then look into getting some metal shelves.
They sell them at Walmart... got mine for $19 and it holds 250lbs per shelf (has 3 shelves)!
I have 2 divided 10gal tanks on it, one on the top and one on the middle shelf. The bottom shelve is set very low so I can put my beanie baby boxes and supplies there.
They come in bigger 4 and 5 shelves... now I wish I have gotten the 4
As for dividing the tank... After months of trial and error I decided to venture into Home Depot and was very excited to find some white acrylic molding for $2.49 (called: white end cap 8ft). Just cut to size, glue with aq silicone and slide in the craft mesh... so easy and clean looking. If only it came in black to match my mesh