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I have had an unidentified shrimp in my tank for about 5 months. It was mixed in with a shipment of amanos and, when I first purchased it, I thought it was an amano. However, over time, he has grown quite large (about 3 and a half inches) and has gotten more and more aggressive. He seems to be able to change color quite quickly, going from a deep brown to red to clear.

Regardless, he has decimated any and all other shrimp in the tank (except for one amano which he had left alone until last week). But now, it has progressed a bit.

Last night, on my last water change, I did some tank rearranging, and I positioned a piece of driftwood vertically; it now sits only 3 inches below the surface. The shrimp sits perched on top of the driftwood and dives down after the WCMMs, the only other inhabitants in the tank.

Today, I came home from work to find a fish carcass and two fish missing their tails. While my WCMMs have always done some bickering and internal-shoal struggling, they've never caused any actual damage to each other and I believe it is from the shrimp.

Tonight I'm going to put the tank back into the old configuation as that seemed to keep the shrimp rather complacent, but I was hoping if someone could help me identify him.

Photo 1

Photo 2

Forgive the poor picture quality. He's rather skittish and I have a less-than-ideal camera.

Any help would be appreciated.

Joe Potato

I believe someone else found these in a shipment of amanos as well and never got them IDed. Likely a Macrobrachium species and if it gets big enough will prey on small fish. If you don't want to risk it I'd return it or setup a small species tank for it until you can determine how safe or dangerous it is for your other tank.

Yeah, I was figuring it was some sort of Macrobrachium as well. In any event, I now have him established in his own ten gallon tank.

A large shrimp in planted tank with lots of driftwood is not easy to catch.

Joe Potato

Definitely some sort of macrobrachium... sorry he killed all your other shrimp. He'll grab fish, too, if he can, so really it will be best if he's on his own, or you could return him to your LFS where you got him and demand that they take him back since he wiped out all the other shrimp that you bought.

Hoping that there must be a word for everything I mean...

I think I'll keep him. He's grown on me a bit, even through the carnage. He's already taken over his tank. It's kinda funny; he marches across the tank, and looks up at me as if to say "Oi! Back off!"

I'm thinking of getting something a bit more peaceful for the tank, something like a bamboo shrimp.

Joe Potato

Red Claw Shrimp

They are one of the bigger shrimp. As you already know they will take out small shrimp. I have also heard and read that they will eat snails too. That could be a bonus in some peoples case.

If you do a google search for Red Clawed Shrimp I am pretty sure there is more out therer. We had them at work a few months ago. Someone brought them in. Said that he had tons of them because they were breading.

55G Planted tank thread
19G Container Pond
[IMG]http://i4.photobucket.com/albums/y118/Wingsdlc/Ric

Close, Wingsdlc, but I don't think that's him. He's not nearly as mottled like that shrimp seems to be and his tail is a distict red-brown color.

Joe Potato

Good eye! I didn't catch that. I would have to say that they are in the same family though.

55G Planted tank thread
19G Container Pond
[IMG]http://i4.photobucket.com/albums/y118/Wingsdlc/Ric

Tried hunting around but couldn't find your shrimp.

You could try browing this site and see if anything like it turns up during your search.

The red tail is causing some confusion here - usually, the moment I hear of anyone with a rogue shrimp, my first thought is Macrobrachium rosenbergii, which is sometimes imported with Amanos and ends up large enough for the dinner table! But, I've never seen a rosenbergii with a red tail. In other respects, though, your shrimp is definitely a big Macrobrachium, and some species can exceed 12 inches when fully grown ...


Panda Catfish fan and keeper/breeder since Christmas 2002

Some of them have features which resemble mine, Cali, but none of them match perfectly.

Mine most resembles the "Guatemala Shrimp" or the "Indian Shrimp", which is funny because neither of them have defined scientific names. Alas.

As far as the red tail goes, that is very mood dependent. When he's actively foraging or hunting, the red is there. If he's stressed, it disappears. It can be seen in both photos of him that I've posted.

Joe Potato

It's interesting that in the week or so that he's been in his own tank, his coloration has changed. The substrate is considerably lighter than what is in the main tank (by my father's insistance) and now he has a considerable range of dark blues and blacks in his body now as opposed to the reds and browns he previously had. I'll try to snap some pictures of him in the next day or two.

As far as him taking out fish, he's going at a rate of about one every two nights. My dad got some feeder fish for him (despite my protestations as two of them were clearly sick when he got them and the extra stress it put on the bioload forced me to purchase some Cycle as well) and he has whittled down the crop to 0 now.

Joe Potato

Wow, that's pretty cool. The color changes are to be expected, but are very neat to see for yourself. He is clearly a very pampered little shrimp if he's taking out a feeder every two days. Fortunately, most fish diseases will not effect shrimp, so you shouldn't have to worry about that.
I'd love to see more pictures of him. /:'

Hoping that there must be a word for everything I mean...

Well, my father continues to purchase the feeders regardless of what I tell him (under the logic that 'He's a hunter. He needs to hunt.'). In any event, 5 feeders were put in last night. This morning, 2 remained.

I'm having a hard time believing that the shrimp would kill three fish in one night solely for food, as evidenced that I found two floating fish halves this morning. I'm curious if it doesn't have more to do with territorial aggression than actual hunger. That, or he's a murdering sociopath (which has been suggested by my family).

Next time I clean my main tank, I'm going to take out some Java Fern (hardy enough to grow in the ambient light as I can't leave the shrimp's tank light on because he goes ballistic) and give him some more broken lines of sight.

Pictures to follow in a day or two.

Joe Potato

Well, the pictures ain't gonna happen because he molted over the night. When he molts, he goes into hiding for a couple of days (read: half the time after he molts I think his shed husk is actually his dead body because his live body is no where to be found) and since I'm leaving for college on Saturday, I'm probably not going to be able to get the pictures.

Alas.

Still has his healthy appetite. He rips shrimp pellets apart.

Joe Potato

It looks like a juvenile Macrobrachium lar, a wide-ranging Indo-Pacific species found from East Africa to Tahiti (and successfully introduced to Hawaii). Some images of adult specimens can be accessed http://www.h2.dion.ne.jp/~karo/new_page_14.htm. Adult males can reach 40 cm in total length.