It all depends on your budget, if you are very good with water changes then you don't need to spend as much, but if you don't have much time to do constant water changes, than I suggest getting the fx5. I am a sophomore in highschool, and I have a 90 gallon aquarium with an aquaclear 110 and another cheap little in tank filter. I spend on average an hour every Saturday using the gravel vacuum, cleaning the glass and plants, and refilling the aquarium. It also takes me about 5 minuets to do my water tests. I say if you are confident with your water changes than you don't need to spend a lot of money, all the filter does it keep the water moving and pick up random particles, it also is a great place for your beneficial bacteria colonies. But it is mostly on you to suck up all the poop, the filter is just an add on. I know this does not happen often, but you also eliminate the risk of a water leakage with a hang on back filter. The fx5 is not in the aquarium, so there is always that risk