Great tank! I can't recommend a new filter or whatever because i really have no clue, but about aquascaping, IMO it is better if you just build the rock without anything. To get arches and caves, when you buy the rock look for strange shapes and edges. In my 58 i have vanuatu rock witch is loaded with points, bumps, and i dont have a single round shape. A lot of fiji rock is kind of circular and you wont get a desired shape. Keep us posted on your tank, i cant wait to see ow it turns out, and it gives me an idea of how to set up the nano tank i plan on getting. Good luck with your tank.