Arrow Crabs

[kaiser]

I was given 2 arrowcraps today. They are the replacement for a sleeper goby that disappeared after 2 days in the Tank, which in turn was already the replacement for the first sleeper goby did not last no 2 days itself. Guy at the LFS seems to think the bristleworms may have gotten to it. He told me the arrow crabs would hold the bristleworm population in check. I guess I am trying to find out if that could be true. Anybody here had any arrow crabs?

[Tim Marvin]

Yes they eat bristleworms.

[kaiser]

So is that a good thing? I usually do a little more research on the critters I get, just this time they gave them to me and I just hard say no to free stuff. What about bristlworms are they or are they not beneficial?

[Tim Marvin]

They are beneficial and the arrows could wipe out the population, but if your tank is 100gallons or bigger I don't see a problem.
P.S. it is very unlikely that the bristleworms got your fish. It is more likely they cleaned up the death scene.

[kaiser]

I got a 125 gallon tank, but I do not have a whole lot of rock in it.

[MikeP]

Most bristleworms are not going to be an issue with preying on fish. The fish could have died and they consumed it but 99% of the bristleworms in our tanks are beneficial detrivores and scavengers. The predatory ones very rarely make it into our tanks.

Having said that did you check outside the tank for the gobies? They are serious jumpers and I have had them find the smallest holes in my hood to shoot out of. The arrow crabs will work to reduce bristleworms but I would say they are much more of a threat to small fish than the worms themselves.

Coral Banded Shrimp are also good for hunting bristleworms if you want to give them a try.

[StephenA]

No way the bristleworms killed the fish.

[matt]

Which lfs is giving you this wonderful advice?

[StephenA]

How many Bristleworms do you have?

[kaiser]

I didn't really buy into the bristleworm idea, but the store that usually does not warranty their marine fish and still willing to replace for a second time is pretty good. I don't know how many worms I have. I know of 1 that is about 8" long.

[StephenA]

My 72gal has 4-5 very long worms (5-8"). And those are just he ones I can see/find. I've never had a problem with them. I've had 2 fish just vanish. But I would say they died and the worms and other cleanup crew guys finished them off. Crabs are the number one killer of small fish.

[Instar]

Arrow crabs may kill very small fish if they can grab them. I've seen them carry small damsels on their horn for a while as if it was a ceremony of some ancient tribe. A huge bristle worm, like 8 inches, can sting a goby and cause some trouble, even death. Its not something they do on purpose, just happens in passing or at ngiht when the goby is buried in the sand and the worm comes passing by when the fish is too shallow. Something likely that killed those gobies are the tentacles of an anemone. Some gobies don't have much sense and will back right into the tentacles and get a leathal sting. Once stung bad enough from either bristle worm spines or tentacles, then the bristle worms will clean up the dead goby and you'll never see the body. When they are first netted from the store and introduced to your tank, their mucous membranes are too thin and damaged to withstand much of any kind of sting and survive. Keep an eye on that shark egg. Don't know what the arrow crabs might do to that.

[StephenA]

I think the anemone is where my missing fish went to. I've lost a small blenny and goby like that.

[kaiser]

After watching these guys last night going after snails and my colt, I just took them back to the LFS. Got a coral instead.