Lost our Sea Hare, Trying to find cause

[Glasswalker]

So we bought a Sea Hare literally one week ago today. It was approx 4" length.

We've been battling hair algae in our tank, I actually have another post in the reef chemistry forum with a ton of parameters, etc. Been battling it for a while.

Anyway, we've seemed to hit a bit of a stand-still with it (not really gaining ground, but not losing any either) and hoped that a sea hare's apetite for the stuff would let us finally get ahead of it.

1. Brought it directly home from the store, about 20min total travel time.
2. Checked store water, was 1.025 exactly, and PH 8.1.
3. Checked my tank, 1.025 exactly, and PH 8.1.
4. Sea hare appeared to be active, moving around in the acclimation box.
5. Used my acclimation box (double siphon water replacement method) and replaced the approx 1.5L of store water with my tank water slowly over about an hour and a half.
6. Placed the sea hare on a rock in our tank and he immediately started munching down, ate a 3" diameter area completely bare. I was impressed.
7. He then crawled off the rock and curled up on the sand.
8. Next day he was crawling all over the glass, munching on a bit of algae here and there.
9. Again after about a full day of activity he went and slept under a rock (not entirely under, just kind of tucked under a slight shelf, fully visible).
10. He continued this routine, going out daily, and roaming the tank. We didn't want to irritate him, so let him do his thing, he never went back to the rocks though.
11. On Thursday, I reached into the tank and moved him back onto a rock, hoping he'd eat more of the hair on the rocks (that's the part that's bad, rest of the tank we can clean by hand quite easily). And he started munching away again. But after about 30min of this he just stopped...
12. Next morning he was in the same place (about 12h later) and hadn't moved.
13. That night I got home, and he had moved to the side of that rock, and was curled up in a small nook in the side of it. He had moved into the flow of the power head near there, so I know he didn't just "fall" there.
14. After 48h of no movement in that spot, we got worried, and I filled the acclimation box with tank water and pulled him out to that just to check on him. He wasn't moving at all. Was no longer "attached" to the rock, didn't react at all to my touch, no defensive reaction, no movement at all. Put him in the acclimator for half an hour, no signs of life.
15. In addition his back had split from the intake siphon, to his exhale siphon. Exposing the shell inside.
16. After a bit longer trying to get some kind of reaction from him, and he never once stuck to the surface, or attached at all. I deemed him a gonner.

I've read about this "back splitting" thing in other threads, but never seemed to get a real answer as to why.

Anyone have any suggestions what could have been the cause?

My parameters are all normal from what I can tell, Obviously something causing the hair to grow, but I'll be danged if I know what it is.

Salinity 1.025
PH 8.1
Nitrates 0
Phosphates 0
Nitrites 0
Ammonia 0
Temp fluctuates between 78 and 81 (depends on time of day, and heaters aren't that accurate)

Montipora coral is happy, Hammer is happy, BTA Anemones are happy (4 of them), Rock Flower Anemone Happy, and all fish are happy.

For more details on parameters, etc, see my thread in chemistry forum:
https://www.reef2reef.com/threads/hydrogen-sulfide-smell-from-tank-related-to-gha.309034/

(by the way, said smell is completely gone, and never did determine what exactly it was)

Here is a pic of the poor little guy with the back split so you can see what I'm describing.

I know some people have a hard time with these, but I'm just trying to understand what could have been the cause so we can try to prevent it in the future.

Thanks in advance for any suggestions.

 

[Irish Reefer]

Prior to where I'm at now w/ my tank I had what could only be considered an algae farm. I ordered a sea hare and driped him for around 1.5 hours. He proceeded to absolutely wreck the algae in my tank to the point where he starved b/c I wasn't paying attention to the lack of algae.

The one I received was around 1 inch, he lived for roughly 3 months and did his job. He got roughly 3-4 inches in length when it was time to flush him.

From what I've seen with them is once they start splitting it's time for them to go as they'll release the toxin from the various types of algae they eat.

If you're having trouble w/ keeping them I'd do my best to start w/ a small one and let them grow up in the tank. I believe when they start splitting it's the end of their life cycle.