I spend lots of time watching the tank. When I work from home I get occasional glimpses all day long :hilarious On other days at least 1/2 hour to an hour for watching and about 10 minutes checking to make sure everything is ok & emptying the skimmer cup.
On weekends there's the 1-4 hours for maintenance - glass cleaning, sponge cleaning, water change, pump cleaning, etc. Sometimes I spread that out during the week.