I think it looks great the way it is! If you aren't happy with the left side, maybe just thicken the plants a bit or add some wood?
A fairly easy way to catch small bottom-dwelling fish is to make a bottle trap. Here:
I suggest baiting it with frozen food. FYI, the easiest way to get the fish out is to just pull the two pieces apart underwater.
I would also suggest adding another otto or two, as they seem happier with company. Maybe you could add Endler's Livebearers when you get the cories out?