Is the top also a double layer of 3/4 plywood? If there is a weakness in that design, it would be the top, which may develop a slight permanent sag in the middle, leaving the tank supported only by the ends of the tank. I find it very hard to find plywood that isn't already warped. Baltic Birch plywood tends to be the most flat, and it also has by far the most beautiful end "grain".
Like your other stand design this one looks like it will look great - excellent proportions.