Hey Lee I used J.E.F fabrication in the woodlands for my 96x40 steel stand.. with good results.. I think dark8ngel had an issue with them.. I was real specific about what I wanted and told them I would be measuring tolerances, checking welds, etc. when I picked it up.. A LOT of communication with the owner who is an Aggie like me..
.. they had to grind a few welds a little more when I picked it up but everything was square and spot on dimension wise.
I used precision powder coating to seal it.. if you powder coat be sure they use zinc as as part of the process.. I don't remember the exact details.. I think as a primer before the actual powder coating. They need to know it will be a humid saltwater environment..
Another option you might consider is aluminum tubing and anodizing vs. steel and painting/powder coating. Its lighter and although aluminum will corrode it holds up better to saltwater. Also more expensive..
Regardless of who you use or what material you choose for construction...
I would draw up a dimensional drawing with tolerances, be very specific about weld cleanup, no open ends, gusseting etc. Make sure they know it is for an aquarium and that it cannot be out of square etc.. So that you end up with stand suitable for holding an aquarium vs. a work bench.
