If that frame is built out of 4x4's it will be a flip of the coin as to what weighs more, the stand or the empty tank. If you get tired of aquatics you could always sell the frame to the Army Corp of Engineers, you could shore up a bridge with that! I've seen people use a piece of 4x4 as a makeshift jackstand, in theory that frame could hold 2 1/2 full size pickup trucks. You need a bigger tank for that impressive overbuild.
While most of my building is for fishroom racks, anything from little 5's & 10's to a 3'x10' platform that holds 260 gallons of tanks I did have to do a show stand just to make sure I could. BTW that platform has six 4x4 legs, 2x6 perimeter frame with 2x4 stringers every 18", sits almost 4' up above a couple 150 gallon tubs. I did a stand for a 65 years ago, 2x4 frame, skinned with finished 1 side plywood;
You can do a lot with stock millwork for the trim, it hides things for folks like me who do carpentry out of necessity not as a trade. Pretty sure that's a medium oak stain with a couple coats of satin poly, doors depend on if you have room in the front for swing, or more room to the side to slide. As far as the top, after 10 years the humidity is taking its toll on the plywood, it's starting to delaminate. The wood is the easy part, matching the stain is going to take some messing around. I'd go with hardwood plank, but then weight becomes an issue, with a 2x2 frame it already weighs about 60 pounds;
Quick WIP pic of the rack I mentioned previously, back legs are lag bolted to the floor joists above;
Looking at the framework for that stand I'm not going to worry about the floor you're putting it on, if it isn't concrete you've probably shored it up with half a dozen 8x8 posts!