Convenience: Make all the water whenever you want to instead of running to the local fish store if something goes wrong such as tank leaks or if you need large water changes.
Cost: Fish Stores tend to get costly when you buy per the gallon. Plus time and energy is wasted in going through the whole process of going to the local fish store, filling up their jugs, loading their jugs, driving back, and then unloading the jugs.
Control: When you own a system you know exactly when to change the filters, the exact water quality, and how much water you need. No need to count on someone else to keep up their system, you’ll know when its time to change the filters and how clean the water is coming out of the system.