Nope, no reason. It just says on the bag to use 1 1/2 - 2 pounds of gravel per gallon. I bought two 5 pound bags so I just used it all because I didn't want like half a bag of gravel left over. It really doesn't matter, I'm sure. It's just what you prefer!
It might mean more detritus can get caught in there, requiring a deeper cleaning with the siphon, but nothing too extreme. To be honest, it takes away a little of the depth from the water. Bettas don't exactly like a lot of depth...if I were to put one in a 5-gallon hex, I think I might mimic our dear OP's example!
That is a very nice tank! I can't wait to upgrade!!
One quick question, tho, and I know I'm just a noob to the board and the obsession, but is that enough surface space for your Betta to go up to the top of the tank, what with all the plants?
No disrespect, just curious.
Nice, nice tank.
No disrespect at all! Like Mister Sparkle said, I am sure there is enough surface space. It might be difficult to see in the pictures because the angles distort the view a bit, but the plants are not covering the entire surface.
And thanks! I love working at my desk with the tank light on. It's very pretty.