isn't it too many fish for such a small aquarium? especially with goldfish, as far as i remember you are supposed to have 20 gallons for the first fish and then 10 gallons for each subsequent fish
I have seen a coffe table in France one day, which was an aquarium as well, only 3 cm high, and about 2by2 meters wide, that was pretty impressive, obviously, only small fishes in it.