Sea Hare Mystery - vibrated into the 4th dimension?

[jessezm]

Hey gang, here's a curious one... I added a sea hare to munch on some nuisance algae in my 45g frag tank (about 90g total water in the system). There wasn't too much, but there are a lot of acro frags and colonies and I didn't want the GHA growing at the base and irritating the corals.

I was a bit nervous because of the 2X MP40s and 3 other powerheads in the tank, but I figured I'd observe it for a few days closely to make sure it wasn't a problem.

the thing went right to town for the first several days and was a model citizen. Then it just vanished. I thought maybe it was just taking a break under some rocks but days went by and nary a sighting.

I've read in a few places that they can be prone to get stuck under rocks when moving sand around, but I don't have any sand in my tank.

This weekend I took out all the rockwork and corals in order to catch a tang, and checked them all thoroughly. There was no evidence of him anywhere!!

Stranger still, even if it just up and died and disintegrated, I would have thought that I would have noticed in such a small volume of water, as I have upwards of 60 SPS frags and colonies, mostly acros and some quite delicate. No nitrates have been detected and phosphates via ULR hanna checker are .02 - .01 ppm. I do run a small amount of GFO and I have a sulfer biodenitrator, but still I would think a 4" sea hare would surely take out a fragile sps tank, no?

Has anyone had this happen to them before, and do you have any possible explanations? I was thinking of trying another one, but I'd like to figure out what happened to the first one first...

 

[jessezm]

Other details:
SG: 1.025
Temp: 78-79f
pH: 8.00 - 8.2
Alk: 7.5 dKh
Ca: 500 ppm
Mg: 1325 ppm
No3: undetectable with Salifert kit
Po4: .01 - .02 with ULR hanna checker

Equipment: RO Regal 250-int skimmer, korallin 3002 biodenitrator, korallin 1502 calcium reactor, giesemann 60" aurora t5/Led hybrid, 2X mp40s, XF250 gyre, 2X coralife wavemakers, Eshopps 300-adv sump and 33 gal pond liner remote refugium

No sea hare found stuck in any plumbing or in the refugium either, in case you were wondering

 

[Halal Hotdog]

Was going to ask about the sump, but it seems like you checked that already. How long had it been between the last time you saw it and when you check under all the rocks? It is possible that it died and disintegrated into nothingness. I would imagine you should have seen something though, especially if you have no sand.

 

[jessezm]

It was a solid week, so it would have been long enough for it to get consumed I guess... Just don't know why it would have died since it was so active and healthy looking, and everything else in the tank looks fine.

 

[Halal Hotdog]

I have had a sea hare in a nano tank 3 years ago. He was doing great, eating well, then all of a sudden he was dead. No rhyme or
reason to why he died. While researching I did discover that their lifespans are not terribly long. I got him out the day he died so did not witness the decomposition, however I would imagine a week might be enough time.

 

[jessezm]

I was so afraid a sea hare death would be the end of my acros but gosh, they didn't even blink I don't think. If it did die (which it must have), I guess heavy skimming, GAC and GFO, and an adequate CUC maybe prevented catastrophe?

 

[Halal Hotdog]

I personally do not believe a death of a sea hare always leads to a tank being nuked. If a sea hare is being picked on then it can release some nasties into the water. If not stressed and just dies, then I don't see them harming anything. I find palythoa are the same. If a section just melts away then nothing else in the tank is affected. If I really start bothering a few polyps, the mucus they secrete stresses the entire tank out.

 

[Dennis McGrath]

Maybe crawled out and landed on the floor, then the cat ate it?

 

[jessezm]

Just one of those things I wish I had a definite answer for! I'll go with the cat hypothesis, since I don't have one, and this whole episode's been strange

 

[cristata.reef]

What species is it? And what fish are in the tank with it. Some species like the Dolabella auricularia (AKA Blunt-Ended Sea Hare, Fringed Sea Hare, Dolabella Sea Hare, Massive dog turd that moves, etc) will bury themselves into rock crevices or substrate when threatened, fill with water until turgid and wait there util the threat has passed. Believe it or not, they can be very good at hiding. I've seen several do this in the wild and almost swam right past them, despite the fact that they were pretty much in the open

 

[cristata.reef]

Also if not eating enough they can shrink considerably

 

[jessezm]

It was a Dolebella, based on the pictures I'm looking at online. About 4" in length. There was still plenty of algae it could have been grazing on so I don't think that was it. My tank critters include 4 ocellaris clowns, an orchid dotty back, a watanabei angel, and a yellow tang, none of which ever showed any interest (nor would I expect them to) during the considerable time I observed it eating (there's something wildly satisfying about watching a sea hare mow down GHA...).