I have a unique situation as I would describe it. I first started with a 90 Gal tall, would do normal water changes (15% bi weekly), tank was doing great. I then upgraded to a 120. Switched everything over to the 120, no hiccups, no losses, no outbreaks. Still maintained water changes and normal husbandry.
My wife and I moved 2 hours away, then had to move the tank to my parents place for 3 months until we settled in our house for the time being. The tank move went great. No losses, everything went well. After a month and a half, began seeing some algae issues, I lost a magnificent foxface. I was not cleaning and caring for the tank as much as I was busy on the farm during this time. I could definatly notice housekeeping issues. I then moved the tank to my current house, 20 minutes away from my parents place. This move went very well, no losses. Now I am watching the tank more "normally" and have not experienced any losses or crashes. The tank technically would be 3 years old, but has been in the spot it is in for a year and a half.
I have not had any major algae, knock on wood. Im not sure what I can attribute this all to. In my opinion, this is alot of stress on the tank for the age it is. 95% of the live stock, coral, shrimp, crabs, fish, are all original. have not added any fish for a year, as I am happy with the stocking list.
Over the last 6 months, I have been playing with lighting. I have 2 AI Hydra over a 48" 120g. I havent noticed much increase in growth in anything but my Anemones. Theses things have doubled in size. I went from approx 35% across the board, to 50% across the board on all channels. Feeding has remained the same. I havent changed dosing at all since the start, still a 3 part dosing to maintain levels.
My Alk is 10, Cal 400, Mag 1320 or so. I have started Carbon dosing with Vodka in the last 3 months, have enjoyed more polyp extension and coloration. Not sure if this is to do with Vodka or increased lighting.
I think the main thing I attribute my success to is maintaining equipment in the sump and tank. Not just water changes, but cleaning power heads regularly in vinegar solution, cleaning and adjusting skimmer, cleaning and replacing bulb on UV, vacuuming out bottom of sump, testing and adjusting dosing. Wiping down the lenses on lights, just keeping a clean system.
One thing that I havent mentioned, is my RO system where I live, will only give me 32 out of the membrane. The water out of DI canisters, only lasts about 100 gallons of RODI water, I have just learnt to deal with the 32 PPM of TDS in my ro water, and have not noticed any issue with that in the last year and a half.
Hope this helps,