Big Beasty

[chris348]

Found this in the tank this morning, dead.

It measured about an inch to an inch and half in size. After recent deaths of some fish, shrimps and now hermit crabs, i found it laying in the sand alongside a half eaten Blue legged hermit crab. Anyone able to identify it ? and let me know if it could have been the culprit?

<a href="http/i273.photobucket.com/albums/jj222/c..._2008/thing.jpg" target="_blank">http/i273.photobucket.com/albums/jj222/c..._2008/thing.jpg</a>


TRY THIS

http/i273.photobucket.com/albums/jj222/c..._2008/thing.jpg

 

[snoopyfrench87]

image doesnt work

 

[Colin_T]

Just looks like a bristle worm
Do you hear any clicking in the tank at night? If so you could have a mantis shrimp that is hunting things. Otherwise it is water quality or a disease but disease would normally affect fish or crustaceans, not both.

 

[chris348]

Have been doing the listening to the tank at nights, and have never heard any such noises.

The only remaining fish is a blue cheeked goby and he it seems is very happy. As are the pulse corals, yellow polyps and feather. Very intruiging and i am slowly pulling my hair out with it lol....

 

[Colin_T]

Have all the creatures that died been missing parts, like they have been attacked?
You might have a big ol crab in the tank that is eating things. It would kill anything smaller than it and if it trapped a fish in the rocks would kill and eat that too. Otherwise take some water to the LFS and get the it tested for salinity, PH and the other usual stuff. And check the temperature, make sure the thermometer is reading correctly.

 

[chris348]

Thanks Colin, your a star.

Have taken the water to the LFS and all checks out solid, water temps are bang on too. The funny thing about the fish was i could not physically see any damage to them, however, about 2 weeks ago, we were watching the cleaner shrimp up at the top and towards the back of the LR, only for its head to come out flying one way and its body the other !!!

Would a Eunice worm be able to do this Colin ?

 

[Colin_T]

Ooh that's a bad sign when cleaner shrimp get decapitated in the tank.

Not sure what a Eunice worm is but there are plenty of predatory worms that will catch and kill things in the tank. However they usually live in the sand and if they are big enough to kill a cleaner shrimp I would think you would see it sooner or later. They also like to keep their prey to feed on.

You could try tying a piece of squid or prawn to some fishing line and putting it in the tank at night just after lights out. Let it sink to the bottom near the front of the tank, then lift it up an inch off the bottom. Then sit back and see if anything comes looking for it. Use a torch to check the prawn or squid to see if something is feeding on it.

 

[chris348]

Ok tried hanging a raw prawn from some fishing line and the hermit crabs went for it after a while, also though just before it got completely dark, what i can only describe as a flea? black and coming out from the bottom right of the tank, darted around the prawn. I put the light back on and the "flea" darted off under the rocks again.

I have now made the trap as shown on this forum and its armed with more prawn.

Lets see what happens in the morning ???

How long should i think about leaving it in ?

 

[Colin_T]

the dark flea thing could be a mantis shrimp. They move pretty quickly and will kill anything they can.

If you set up a trap then leave it in for a couple of hours after dark. That should catch whatever it is. If you leave a big piece of prawn in the tank overnight it will probably cause an ammonia reading so only use a small piece (no bigger than your little finger nail). A small piece will still create a bit of ammonia but nowhere near as much, and it will be adequate to attract whatever is in the tank.

 

[SkiFletch]

Agreed, sounds like an invert trap is in your future. Could be a predatory Isopod, I've heard of such things. Honestly, mantis shirmp large enough to take down fish are rare, its more often a crab or some other mysterious invert.

 

[chris348]

Ok had the trap set up for about 6 hours, came down this morning and inside were 5 minute flea like beasties, for want of a better word.

Measured about 3 - 4 mm in length with a brown and white backing?

Took some pics but not sure if they would be able to show too much.

Your thoughts guys?

If there is anything else in there that shouldn't be, i am hoping now that after taking out 1 larger Mantis Shrimp and 1 possible Eunice Worm (having done some more reading up, i am pretty positive that it is), along with these 5 small critters, what on earth can be in there and how would you go about catching it.

I did have a thought that i should again this evening with the trap and see what that comes up with?

 

[chris348]

This is the best pic i could take. They are really small but you may get some idea of what they are?

http/i273.photobucket.com/albums/jj222/c...08/Beasties.jpg

 

[Colin_T]

If the flea things are on their back in the photo then I would say they are gammaris, (amphipods). These are pretty harmless and occur in most aquariums. They are scavengers that feed primarily on algae and rotting plant matter. They are unlikely to cause problems to the fish or shrimp.

You could have an eel in the tank or a crab as mentioned by SkiFletch. Sometimes small eels come in with live rock and over time they grow. But they would probably eat your shrimp not bite them in half. A crab would snap things in half and then try to eat them.

I would keep the trap set every night for a week or so and see what you catch. Just be sure to monitor the ammonia levels and make sure they aren't getting too high with the food in the trap. And if possible check the trap throughout the night. Most predators come out shortly after dark.

 

[chris348]

Thanks Colin.

Last night i placed the trap on the bottom of the tank, would it be better if i placed it higher up?

 

[Colin_T]

it shouldn't make much difference where the trap is. Try it on the sand sometimes and on the rocks other times.