Daily: Stare at the tank and enjoy it
Several times a week: Wipe down front glass, clean algae with Mag float.
Once a week: Empty and clean skimmer cup, rinse all mechanical filters, fill up ATO reservoir.
Once every 2 weeks: 10% (20 gallons) water change on a 200 gallon system, check salinity in DT.
Once a month: Replace GAC, refill dosing containers, check alk levels. Tank has been running for over 3 years, so I don't check anything else anymore. Unless something looks off.
Every several months or so: Frag overgrowing coral, and give away or throw away the pieces.
As needed: Replace bulbs, replace RODI filters, clean equipment.