[Carl Spackler]

A few months ago a had royal damsel disappear from my tank. I never found the fish or any remnants of it. This past week my Bartletts anthia and two emerald crabs have also gone missing without a trace. My thought was that the anthia flopped out of the tank and made a midnight snack for my cat, but because I'm certain my crabs didn't flop out, I'm not convinced my fish did either. I'm starting to think I have an unwanted guest lurking in my tank preying on my livestock. I found a one inch bristle worm crawling on the side of my tank and quickly removed it about four days ago. Aside from that I haven't seen anything unusual. Has anyone had similar experiences?

 

[zac55g]

I had this same problem happen to my 9in engineer gobie never seen again. I woudnt say the bristle worm had anything to do with it they are benificial to aquariums and only eat dead things if the fish died somehow your clean up crew could have ate it.

 

[miyzfrider]

Not sure about your fish, but I know my emerald has gone AWOL for days, then all of the sudden appears. They are masters of hiding. Don't know what amount of rock you have, or if it has some decent holes in it, but they may just be hiding out.

Hope you figure it out.

 

[nanoryan89]

I'd say your damsel died and he was eaten/ cleaned up by your cuc. It's a fast and easy snack for bristle worms. Especially if you're finding them crawling around in your tank, then you have lots. Which means they're competing for food now.

As for your anthias, i would suggest he jumped and/or he also died and was quickly eaten.

Crabs are different. All of my crabs have gone missing for more then a week at times. Even in an 8g biocube they go missing for quite some time.

Now when it comes to something eating your fish BEFORE they die is a whole new ball game. It could be a crab, worm, octopus (yes it happens). I guess the easiest way to find out would be to put a trap in with some food and see what happens.

 

[Carl Spackler]

Can you elaborate on the trap idea particularly how to set one? I think its worth trying

 

[Paulo]

I had the same happen to me. Finally one night I heard a tapping noise which I thought was a mantis shrimp but never saw it. A few weeks later I looked in later at night and found I had a parasite crab (I think an acro crab) moving my coral around and killing fish. I had to take out every piece of rock and inspect it. I actually had 3 of those bad boys in there. After they were gone, I had no more problems. Things always seemed to disappear at night fo rthe most part. It sucked because I had to closely inpect everything in the tank. These crabs blend in well with rock.

 

[Jessemac]

I had the same happen to me. Finally one night I heard a tapping noise which I thought was a mantis shrimp but never saw it. A few weeks later I looked in later at night and found I had a parasite crab (I think an acro crab) moving my coral around and killing fish. I had to take out every piece of rock and inspect it. I actually had 3 of those bad boys in there. After they were gone, I had no more problems. Things always seemed to disappear at night fo rthe most part. It sucked because I had to closely inpect everything in the tank. These crabs blend in well with rock.

If it was an Acro crab, it wouldn't have harmed any fish let alone kill one. Acro crabs tend to spend there entire life within the branches of Acropora corals. Not to mention they stay relatively small. There are many crabs however that are very much capable of catching and killing fish.
I would guess that guess that the disapearing fish most likely died and were eaten by your CUC (snails, Hermits, Emerald crabs, bristle worms, ect.). The crabs are probably in there somewhere. Emerald crabs are masters of disapearing. Though, if there isn't enough food i.e. LR to pick off of. They will starve and die off as well. If you think you have a pest of sorts. Spend a couple nights with a red light peering into your tank for hours on end. You will probably seem whatever it is, if there is something. As for the traps, there are ones you can buy or you can make one out of a 1L bottle. Cut the top off right where it starts to tapper up to the cap, filled it around and snug it inside the bottle. You may have to cut the spout off depending on how big the opening needs to be to catch whatever you are trying to catch. How long have these fish been in the system? What are your Params like? Best of luck.

 

[McPuff]

I agree about the crabs. Just keep an eye out for them and they may reappear. As for the fish, the most likely idea is that they died and were eaten by the invert population... and some other fish may have helped as well.

But, I also wonder if you have any brittle stars or serpent stars? Sometimes you can get one that has a taste for fish. This happened to me once and it ended up killing about 4 different fish before I finally figured it out and removed it. These are also common hitchhikers so you may have one without knowing it. The bigger ones will generally be visible though at some point or another. Whatever the problem is I hope you figure it out and rectify the situation. Good luck.

 

[Higgy]

Do you hear any snapping or popping noises after the lights go out?

 

[Carl Spackler]

I found my emerald crabs, they are indeed very good at hiding. I think my next purchase will be a red light.

 

[nanoryan89]

+1 on the red light purchase.

And since your crabs are still alive. I'd say your fish are just dying off/ jumping.
If you still think you have a pest problem, like someone else said, make a trap out of a bottle. And bait it with a chunk of food.