Old Newbie could use some help with dying brain coral

[Kjosephscott]

Hello RC,

I have been a closet reef aquarium owner for 10 years. I got a 120 Gal with various fish and coral from a friend getting deployed 10 years ago. I somehow have managed to keep the thing alive through three moves and even 9 months "in storage" with a friend who never changed the water and just made sure it was plugged in while I was in the hospital. I have most of the original corals and even a Gobi from the original owner. I moved it and stabilized it in my new home and it has been recovering nicely for 5 months. I was being a little stupid post hospital and bought a some new fish, some shrooms and some zooanthids right after I moved it. No problems and no changes for 4 months. 10-15% water changes every week because I have to hand carry the water. Last Sunday after being out of town for 4 days I came home to a half dollar sized fresh dead zone on my brain coral. In 5 days it has quadrupled in size. Pics below. Please don't ask about my levels. I only know my salinity and it is within range. If anyone wants to recommend a good test kit, the one I have is 14 years old. So please no judging as I have managed to fake this for 10 years. Anyone have any obvious answers/solutions/recommended actions for me? Sorry if I should have jumped to a different thread. I have not figured that part our yet either.