Depends on what you consider work. The actual work ( I have a 125 gallon tank)
Daily, 5 minutes cleaning the glass with a magnetic cleaner
Daily, 5 minutes to ??? checking on the tank inhabitants (not really work)
Every 2 -3 days 10 minutes preparing food (remove from freezer, thaw in tank water)
Feeding time is also observation time to check on those that don't normally come out.
Every 2 weeks, 2 hours aprox. to prepare and complete a PWC
of 20-25 gallons
This includes doing water tests, cleaning the skimmer, checking all the hoses, cleaning PH's that may need it, etc.
Every 3-4 weeks 1 hour spent setting up and taking down the RODI
unit to make a 45 gallon drum of top off water. One of the PWCs is done at this time too so all I have to do is move the output hose from 1 container to another.
I'm sure I spend a lot more time than that, like when I notice that the clam or a coral was knocked on its side by a large turbo snail, and I then place it upright again.
Family and friends will tell you I spend a lot more time than that, but it's not work. There's also the time I spend here.