Things went down south lately. We have been on vacation for 2 weeks in June. Which is not too long and I prepared everything the way I always did. Problem here was: it was cold when we left and weather forcast did not say anything bad. But two days after we had left the temperatures went up from 15-16C to 35C in 2 days and stayed there for the full two weeks. With bad thunderstorms every evening so I could not even tell somebody to just open a window to get some ventilation going. Yeah thanks weather forecasters for noticing this heatwave one day before it actually happened.
So water temperature went up 2-3C each day reaching 30C within a couple of days and I could not do very much. I instructed the person looking after my tank every once in a while to prepare some frozen RODI water and throw it into the sump. It did not help a lot but at least it helped a bit and temperature stayed at around 28-30C. Which is high but not life threatening ... You would think. Anyway. She sent me pictures regularely and all has been fine. Especially since all coral have been growing like crazy. All SPS showed looong growth tips with my montis outdoing it by having tips of up to 1cm. LPS where pumped to the max and it looked as if they are about to just pop. Never saw my Fungia more inflated than that.
phew...what a great look and I had such luck. Yeah ... No. I came home, did a 10% water exchange to get out the gunk out that accumulated during that time. Adjusted water parameters where needed (especially PO4 and NO3) and went on with normal maintenance. Measured NO3 and PO4 daily to keep it under control as well.
Just like 2 weeks later things started to go south rapidly. 50% of my LPS started to "shed skin" like somebody scrubbed them with a metal brush. ALL my SPS (except 2 Montis) got unstoppable STN or started going white all together within a week even though ICP and N-DOC came back perfect
There was nothing I could do and nothing I knew that I could do really since parameters have been perfect. Tried fragging, increasing flow, monitored parameters daily. Added some aminos. Did another ICP in case some value might have been elevated even though I had just done one right after coming back from my vacation.
TL;DR: I lost all Acropora. My 9 year old Seriatopora which was a joy since it lived perfectly fine through everything I was throwing at her during the first couple of years also died within two weeks. Before that it doubled in size every 2-3 Month. The LPS' that died have also been in my tank for 7-8 years. The Seria and those old LPS did grow so well that I used their frags to refinance almost all of my other corals.
I think I have lost between 1.5-2k Euro in Corals here and within 3 weeks of that growth-frenzy and no way of stopping it, too
What also happened within this month (as you can see in the photos) was a short but messy and hefty algae bloom. Never seen anything that fast. Most coral had algae growing out of their polyps just days before the STN/bleaching started as well.
The algae mess is almost over again but I am still battling some Ghost Algae and the occasional "bacterial brown cotton" even though I do not dose anything fancy and have PO4 of 0.01-0.04 most of the time. The only thing a tad low is NO3. But I mostly only dose NH and there might not be enough time for NO3 to be created.
I am restocking now. And I also took the almost coral free time to change my t5 bulbs which have been in there 8 months by then.
Before that I was using:
3 x ATI B+
2 x ATI Coral +
1 x ATI AB Special
Now I am trying this combination:
4 x ATI B+
1 x Actinic
1 x 865/6500k daylight bulb
Also I am using this mess to go full "Outer Reef" with some LPS around the bottom.
I went from 2 x Gyre xf 330, to 2 x xf350 als main pumps and put the xf330 to the back.
Here are some photos of some dying corals:
How it looks now:
There is still a bit off an algae mess and it is a bit empty. But Algae are under control and receding. Still a bit of a new ugly phase again

My fungia in the front is recovering well. The green slime appeared on the sand but I have a planned 10% exchange today and they will be siphoned out.
I have also made the fans a permanent addition to the tank. Before that I only installed them when needed. Which did not happen more often than once every couple of years and always sometimes in late August and NEVER in early June. But with climate going crazy I might need them more often and more irregularly. I control them via my "AquaMedic T Controller Twin" to start whenever temperature is 0.2C above normal (25.5C). I also used the opportunity to redesign the fan holder and the 3D printer files and some assembly instructions can be found here if anyone is interested:
https://www.thingiverse.com/thing:4919753
We'll see how it goes from here....