Commercially made wood stands are not made out of pressure treated wood, at least none I've seen. Real cheap ones are made of composition wood, avoid these. A little bit of moisture, & they will warp & fall apart. I looked at plenty before I built my own.
Most all the commercially made stands I've seen are made of 1"x2" & 1"x3" lumber for the frame & support members. I do not trust this to hold structurally for the long term. Rotting is not the point, if you are continually getting the stand wet enough for solid pine to rot, you are getting a lot of water on the stand, your floor, and whatever else may be under the floor when that amount of water leaks through. Size of the support members, as well as the lack of enough large enough screws made me leery. I believe in overbuilding things for the worst case scenario, like a nephew with a big wheel ramming the side of the stand.
I built my own for a 65 with 2"x4" framing & 1/2" finished 1 side plywood for the outside.
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/www.fishforums.net/index.php?showtopic=106692&hl= shows racks in my fishroom, built with pressure treated 2x4's. The 65 on the bottom is the same construction underneath. Pressure treated lumber is what is used to build decks outdoors. The fishroom racks get soaked once in a while, that is the reason they are in the basement. I imagine I'll get a good 20 years out of them, as that lumber is designed for outdoor use.
Seeing as your family is in the furniture business, ask dad to get a solidly built buffet cabinet the size of your tank, or maybe a little bigger. A 20 long comes in around 225 pounds full, add a little more for gravel & other decorations. Any decently made piece of furniture should be able to hold this, I kept a 20 long on an old dresser a while back.
If you do decide to go the metal stand route, get one that comes already assembled, and welded. The bolt together ones are nowhere near as sturdy. Metal does rust, so keep an eye out for that.
Tolak