OK, I'll take a shot:
Living in Florida, if your home is heavily air-conditioned and humidity levels remain stable for most of the year as a result, you shouldn't see much warping.
You would be correct (about the humidity), at least short of sustained power failures from a hurricane, but those are likely to flood the tank anyway.
The big plus for biscuits, dowels, nails, other fasteners is that the joint isn't 100% dependent on the integrity of a thin line of glue through the seasons. In the case of biscuits they also add more surface area that isn't in the same plane as the mitered faces of the frame components and swell within the biscuit's joint.
I'm farm-handy. By that I mean I can build strong things with rough cut wood, and occasionally put up some trim in the house to paint. This is my first foray into real furniture. I say that as a prelude to....
Would someone who has never tried one be better off with, or without, a biscuit cutter to do this?
I can get a 45 simple planar miter to work OK. I just have visions of me using a biscuit jointer and having these really strong boards that are 1/8th off from aligning (or something like that).
It sounds like you're trying to get to an easily-removable panel that simply adorns the 3 visible sides of the stand?
Well, 4 sides, but 1 side is going to be drawers (I just bought unfinished ones that were the right size to slide into the hole, and will trim around it with matching boards.
The tank is sitting in the middle of our living room, all 6' x 6' x 2' of it.
Come up with some sort of a "tray" or slot along the front and sides of the stand that the panels will sit in. They can be loosely fastened at the top with a wooden cam knob or removable retainer of some sort at the top.
Even if nothing more than a bent piece of metal that doesn't stick out much I could do the bottom, but where could I find samples of the top -- I've tried home depot and Lowes and didn't see anything. Or are you saying I need to shape something (somehow)?