I am getting a freshwater fish tank and it is 55 gallons, but a square shape. I was wondering how much gravel should go into it, even though it isn't a rectangle? The dimensions are 25.5 by 24.5 by 24.5
Based on the cubic inches, I believe that's a bit bigger than a 55g?? That's an odd size. Is it a custom built tank? 11520 cu/in for a conventional 55g, vs. 15306 for yours.
Get yourself two bags of pea gravel from the garden dept. of Lowes of the likes. It's under $3/bag, vs. 10x that for pet store aquarium gravel. You'll probably only need 1.5 bags, maybe less.
I also tried the white marble chips from Lowes. Looks AWESOME when new, but looks like a dirty white carpet after a few weeks.
FWIW, keeping live plants isn't overly expensive or time consuming. Just takes a bit more planning and consideration of setup. (proper lighting, suitable substrate, need for a carbon source, etc)