I’m coming to my first 6 months mark, and I’m glad I’d started with fish first. Beyond the initial cycling, you have to maintain the big 3, ALK, CAL & MAG, as well as to NO3 and PO4. Unless you’re a season Reefer, enjoy your first 6 months experimenting with various equipments and thoughts to find your tank’s sweet spot, then move on to corals. Having fishes itself can be a challenge, especially with QT and compatibility.