this is going to be brought up often, and correctly so.looks like there is no support at the outside edges of the tank. The 2x4 that goes from the bottom to the top looks as if it's inside of the 2x4 which is running along the edge instead of under it. This gives the impression that only screws are holding up this tank at the outside edges.
However, since the tank is acrylic and doesn't have a rim I'm not sure if it's as big a deal since the weight should be distributed throughout the entire bottom of the tank.
Though, to be more on point; the reason that this is usually such a concern is that the weight ends up being supported only by the screws. And the sheer rating of the screws ends up being less than the compression rating of the vertical 2x4. However... in this case, with the full bottom being on the plywood some of the weight is going to be distributed to the 2x4's.
I'd think it was fine in this case, but it's still not something a lot of folks would do. You typically want a 2x4 at each corner to appropriately take the weight.
the tank itself is wonderful. you did an excellent job.