Hellow i want to buy the nyos 120 skimmer my aquarium will be fo but i plan to have a lot of fish in my aquarium is the 120 skimmer will fit for me my aquarium? will be 120 cm long 60 cm depth and wide but i dont know how much water will be for real because we have sump overflow box and rocks no sand for me so do you think the 120 nyos skimmer will fit or to buy the 160?