Since you have a busy schedule, my suggestion like what others already have posted is to decrease stock and increase water changes. I would usually say change 30-40% a week but oscars are notoriously messy fish and you may have to do twice a week. Get yourself a good test set to check amm/nitrite/nitrates and test before you change water. This should determine how often you should change your water. Trash the bucket for water changes and get a hose. This should significantly decrease maintenance time. 15 mins max to drain and fill. Also get some seachem safe. It's cheaper in the long run, and since your in college, I'm sure money is tight. If you have the money fx5 are great, but like previous poster mentioned, it does not replace water changes and its more time consuming to clean then HOB filters. And since time is an issue, you may not clean it as often as it needs to be. Also look in pothos to help keep nitrates in check. Very easy and cheap, just clean them and stick them in a HOB filter.
