Six-Line Wrasse Died and Half of SPS STN overnight

[educatedreefer]

So my tank had a slight crash after my six-line wrasse died underneath the rockwork and a majority of my SPS RTN’d overnight.
Woke up to that unsettling, familiar stench of dead fish so had to frag what I could, perform a large water change, and lower my light intensity until my corals get less stressed by the sudden change in parameters.
Had to leave for work in the morning so didn’t get to test my parameters but was able to put in new carbon, WC, and save frags.

Any tips or advice on what to do next or reasons why my wrasse (who was plump, fat, and healthy) suddenly decided to die?

Only have a Scopus tang, two clownfish, and a Pink spotted goby in my 150g that is SPS dominated. No leathers (so toxins out of the question) although I did put my mushrooms in a small basket full of hermit crabs in order to get them to clean off the algae from the rock they were attached to.

Maybe the mushrooms released toxins that killed the wrasse, or maybe it died under mysterious circumstances, and increased nutrients that RTNd my SPS colonies?

Kind of bummed that I have to rescape my tank and lost more than half my SPS colonies.

 

[T-J]

I have a feeling something else is going on here. A 150g tank should have no problem handling a dead 6 line wrasse. I've had fish die in my 120g tank and I never take them out (if I can even find them). I let the CUC do its job. No crashes. No RTN, etc.
I would start with a full test of all parameters.

 

[AlexandraDreadlocksPanda]

One strong theory as towards the cause of STN is that it is the Vibrio bacteria that causes it… this is often found in quantity in fish intestines… However, whilst feasible, I don’t think it’s the only thing at play here. IF the two things are linked, then my most likely suspects are:

•Acropora were already stressed and pollution event tipped them over the edge
•Sixline had been keeping down pest numbers of something. Although you thought it was OK, may not have been as active over last few days in this respect.

HOWEVER, I am also wary of automatically linking the fish death and the STN. Without supporting data, it is nothing more than coincidental. 150g is a LOT of water to be affected by the death of one small fish, it would have to be in a fairly critical state for this to happen imho.
As T-j wisely stated, test. And if you don’t already, log the data whether with an app, pencil and paper etc… only by long term monitoring can you find out what is going on in your tank, and know when something is (or has been) changing. If you don’t know what’s wrong, you can’t fix it!