Fish mystery - at a loss for ideas

[popcorn]

Hi guys. Long time, no post. But I'm at a bit of a loss as to what's going on here.
Ok, I'm at wits end here.

Background: This is a 135, plumbed into 20 fuge, 30 sump. This tank has been up since 2001 (upgrade from a tank setup in '99.) 350 lbs LR. Lots of corals, mixed LPS/softie, clean-up crew is mostly snails, a cleaner shrimp, etc. Fish are listed below. No signs of disease for years, no new LR for about 2 years.

About 3 months ago, we lost our yellow tang mysteriously. It just disappeared one night and didn't show up for dinner the next day. We brushed it off as "one of those things." We'd had him for several months after rescuing him and he was a sturdy, strong little fish.

A week and a half later, I stumbled on a beautiful Powder Blue *that was eating* for an amazing sale price. Since I didn't know what happened to the yellow, I went for it. Fine for 3-4 days and mysteriously disappears. Again, no sign of a body.

Too much of a coincidence. We pulled out our two really large red brittle stars, thinking that one of them was the culprit. Added nothing for 2 months.

Other fish:
6 yellow-tail blue damsels
1 neon dottyback
1 gold-stripe maroon
1 lawnmower blenny

None showed any aggression towards either the yellow or the PBT.

Now the twist. About 2 weeks ago, I was again at the LFS, and saw a stunning sailfin. Knowing that the brittle stars weren't a problem anymore, I brought home the little guy. Ate like a horse, got along as far as I could tell with everyone else, even though he was pretty small. (3")

Last night he was hiding, but swimming. This morning, he was lying on the sand breathing heavily. We pulled him out, hastily set up a q-tank and watched. He was very weakly swimming, and was mostly tossed around by the current. It looked as though he'd been attacked, but it was hard to tell since they excrete so much slime when stressed.

He died about an hour later.

Since this is the first one I've had a body for, I'm trying to figure out what is going on.

Here are my questions:
1. What does a mantis attack look like? That's the first thing that we thought of.

2. We haven't added any rock for several years. How the heck... No clicking sounds either.

3. What other predators could be lurking in there? We've lost no other fish. A pepp went missing a couple of months ago, but it might just be hiding. I haven't actually looked for it...

4. It sure doesn't look like fish aggression, but I can't be sure. The yellow was actually in the same tank with the dottyback at the LFS for a LONG time, and they swam together... and lived peacefully for almost a year, (with the damsels) so I doubt it's that. The Maroon doesn't seem to care, and stays around the top of the tank (by her xenia.) The damsels fight among themselves. Yes, aggressive, but all the tangs were of different colors and body shapes.

5. When do I throw my hands up and accept that I'll never be able to keep another tang in this tank?

I'm really, really upset at loosing yet another - especially given the history. I just don't know what's going on.

I did take some pics of the sailfin - no gross injuries, other than a .5-1cm rip in his top fin. There might be some tearing of the flesh on one flank, right by the pectoral fin - it's just really hard to tell. It really looks more like an abrasion - no big chunks missing.

Thoughts? I'm at a loss. (And I have 50 people coming over for a local club meeting today. So much for showing off my new pride and joy. sniff... sniff... )

Thanks guys,
Danielle

[Reefland]

Hi popcorn!

I don't think it is a mantis, it would have shown it's terror somewhere before I would think. I'm curious, were these recent fish purchased from the same place?

[popcorn]

Nope. The latter two tangs did come from the same place, but it's a very reputable shop. The first we'd had for almost a year. The PBT had been at the LFS for 2-3 weeks doing fine (maybe longer). The sailfin we'd had for about 2 weeks, and it was doing beautifully. No red marks on the sailfin, though, if you're thinking cyanide.

The only reason we were thinking mantis is that a tiny one could have hitchhiked in years ago and just now gotten big enough to take out a tang.

Ironically enough, I was placing a new frag last night after the meeting, and a pointy claw jammed the frag back out of the hole I'd set it in. I got the Mag light, and lo and behold, there's a hairy, yellow-green crab in there with black stripes on pointed claws. Never seen him before, but I don't know if he's big enough to have taken out the tangs. He looked like an emerald crab gone bad, or something.

Either way, we have a crab trap in now. (I've managed to catch some hermits so far... ) He's still in the same rock, so if it comes down to it, I'll tear apart the rockwork and FW dip him.

But that's an amazing update - and we're really lucky to have discovered him. I just have no idea how it got in, where it came from, or if it's really the culprit.

Danielle

[reefrunner69]

No clicking sounds either.

Not all mantis click ;)
But I agree it doesn't sound like a mantis.

I did take some pics of the sailfin - no gross injuries, other than a .5-1cm rip in his top fin. There might be some tearing of the flesh on one flank, right by the pectoral fin - it's just really hard to tell. It really looks more like an abrasion - no big chunks missing.

It is entirely possible these injuries occured after the fish had succumbed to whatever ailment it is. For years there has been a mystery for most reefers trying to add another fish to an established tank. I have never heard a theory I found to be overly accurate, for me it has always remained a mystery. My first suspicion would be (if we accept that the yellow tangs death is unrelated to the other two deaths) aggression from the damsels after the light goes out and the new tangs were looking for a place to sleep. My next suspicion would be low O2 levels.