Questions about Tuxedo Urchins

[Royal_Reef]

I wanted to get your options on what could of caused my red tuxedo urchin to release this white stuff from its head. Then shortly after dying. I woke up on Monday and saw my urchin releasing something. I couldn't tell what it was I thought it was releasing something to possibly breed.

I was in a rush to leave for work, so I didn't have time to look into it. I did how ever get some pictures and videos, If you look at the picture above. There's a white spot on the top of what I like to think it's head. It started coming out like crazy, I recorded it and rushed out the house to avoided being late for work.

Two days later I found it dead, my emerald crab was having it for lunch. Is this normal behavior before an urchin dies? I never experienced something like this with my other urchins so this is new to me. I thought it was spawning or something. The only thing I could think of is that on Saturday I did a 80% water change, it was over due. Normally I do a water change once a week about 25 % I moved some stuff around to get organized and started to do some wear maintenance.

I moved my DOS and airline tubes around and cut the extra line that had with Alk and Calcium in them. It did pour into my tank about 6 mls of solution into the back chamber when I cut the line. I noticed a huge change in the tank, some of the zoathids and LPS were closed up Sunday morning. I did another 10% water change and things were back to normal kinda.

The only thing I could think of is that the Alk or Calcium change might of unbalanced the tank enough to cause the urchin to die. I normally dose 5mls of each solution throughout the day on a schedule. It's a 40G system so I think the addition 5 mls was to much. I took out my Hanna test kits and tested for Alk which was at 8 and Ca at 450.

The weird thing is that I have another blue tuxedo urchin in the tank and it's fine. I moved it to my 13.5 Fluval for now but I'm confused. Let me know what you think?

Thanks in advance !!

Below is a link to my instagram showing the video hopefully the link works.

https://instagram.com/p/BYyke8Qnbhi/

 

[KJ]

It is a spawning event. I have 2 blue tuxedo urchins that does this at the same time sometimes after I do a water change.
It can also be a sign of stress.

 

[spiraling]

It can also be a sign of stress. When I first got mine it did that and then settled in.
The extra addition of alk could have caused a PH swing. Some creatures are sensitive to that, I'm not sure about the urchins.
I have also heard that they are sensitive to high nitrates.

 

[LobsterOfJustice]

Agreed, spawning can be a response to stress and is often seen after water changes (an 80% change is stressful on sensitive things like urchins). It is also a common last resort before dying... i.e. Urchin thinks it is dying, best to get the genes out to the next generation now.

 

[Royal_Reef]

I appreciate you this information and after looking a bit further the stress on the urchin with the alk over dosing plus the big water change caused the urchin to die.