Brackish Shrimp Id

[Flumpus]

Ok, so about a month and a half ago I put several ghost shrimp in my brackish tank for my puffer and gobies to consume. They loved them, and ate all but one in the first few days... but that one, that one special shrimp is still around, eating my algae (and occasionally stealing my bloodworms from the fish). Of course I don't mind that it eats my algae. He's actually gotten the tank quite clean compared to how it was getting with just me cleaning algae when I did water changes. I'm just curious about a couple things. First, in the picture below, does it look like a rhino/rudolph/redfronted shrimp, like on this page? Secondly, is this a brackish shrimp? If so, anyone have one in their tank? It certainly seems to be thriving, as it's grown uite a bit, and is now a good 2". Here are the best pic I could get...

 

[penguinpimp1990]

really cant tell from that pic but since its doing good and eating a lot of algae Id say its an amano shrimp as ive read somewhere (i could be wrong) that they are sometimes foud in brackish waters. and also will only breed there? (again could be wrong). Although you did buy them as ghost shrimp so its very likely that it is actually a ghost shrimp. Ghosties can live quite comfortably in light brackish conditions. But ghosties are not the algae eaters theyre cracked up to be, true they will graze on it but they are scavengers and prefer other kinds of detrius in the wild. my bet is that its an amano soley on the algae eating

 

[nmonks]

I'm not 100% certain, but I am 80% certain that's a Macrobrachium species. They are mostly large, and many are commercially raised in Asia and the Americas as "giant prawns" for human consumption. They are big (some around 15 cm or so long), potentially predatory, and the males can often be territorial. Some are indeed brackish water, but others do fine in freshwater. Macrobrachium rosenbergi is especially widely sold.

A really good site is this:

http/www.shrimpcrabsandcrayfish.co.uk

Cheers,

Neale

 

[Flumpus]

Hmmmm... judging from a couple pictures on that site, one in particular, I think you may be right nmonks. The only problem I had when trying to match it with other shrimp was the size. It's already about 2", maybe a little larger, and that was bigger than the max size listed for most species that looked similar. I certainly don't want a 6" shrimp walkin' around with a goby in each arm biting their heads off, but I'll keep an eye on it to make sure it doesn't cause any trouble

 

[CFC]

If it is a M.rosenbergi then i suggest you get rid of it fast, i bought one of these for our sons community tank and within a couple of months it grew to around 4 inches long and started eating his fish so i moved it to one of my tanks with some larger fish until it ate a 6" sturgeon catfish (P.sturio) i was growing out so i promptly fed the prawn to my arowana

 

[Flumpus]

Well, it doesn't look like a M.rosenbergi, but another shrimp on that page that's only supposed to be 6cm. If it keeps growing I'm afraid I will have to take it out though, because it's getting pretty big.

 

[nmonks]

With the exception of fan shrimps (family Atyidae) and the algae eating dwarf shrimps of the genus Caradinia, pretty well any shrimp is going to eat any small fish it can overpower. In practical terms, a 6 cm shrimp will probably view a 1 or 2 cm fish (like a small neon) as potential food. Whether or not it can catch it depends on various factors, but fish that swim close to the bottom and especially sleep close to the bottom are obviously most at risk.

The larger Macrobrachium, as CFC points out, are even more dangerous, and should be considred "predatory" as far as choosing tankmates go. While they are fine with larger fish, they simply view smaller fish as prey. Moreover, they are highly territorial, and can be cannibalistic as well. I've seen them mixed with similar sized cichlids in public aquaria, and I'm sure you could keep them with things like plecs, too.

This picture gives you a nice idea of how big they get:

The reason I don't think it's a Caradinia or Neocaradinia shrimp ("algae shrimps") is the size: none of those traded in the hobby seems to exceed 5 cm when mature, and most are far smaller. Macrobrachium species, on the other hand, routinely grow large and fast, and are very hardy.

Is the rostrum (the "snout") serrated (i.e., like a saw)? How robust are the front claws? Macrobrachium -- as the name suggests -- have very sturdy claws, and those of the males are extra long, as well.

Cheers,

Neale

 

[CFC]

Macrobrachium rosenbergi can take prey larger than its self as i found out to my dismay when it ate the P.sturio, a hard lesson learned about not researching and believing the lfs when they said it wouldn't grow bigger than a few inches and was community safe.

 

[Flumpus]

First of all, I've found another thing in the water to be afraid of after that pic nmonks. Secondly, I can't really tell if the rostrum is serated or not. It loves to hide in the plants, and if I make a movement to get closer to the tank to really get a good look, he goes back in and hides. I'm also not sure about the front claws. They are long and it uses them a lot. They do seem fairly robust.

It looks a lot like this, from the page you posted above. That's the one that is supposed to get to 6cm, but I think mine maybe at that now. At this point I'm seriously considering taking it out I think. I'm not worried about it killing my puffer or gobies, I just don't want it to try anything and have one of my fish get injured in it's sleep or something.

 

[nmonks]

I stand corrected!

I think it's a good idea to watch the shrimp carefully. It doesn't look like Macrobrachium rosenbergi, but frankly so many shrimps are imported without any record of their Latin names, don't be at all surprised if it's some totally new.

Bear in mind that most shrimps are relatively harmless towards fish of similar size (consider marine reef tank shrimps). Like snails and plants, the fact people have seen them eating dead fish doesn't mean they actually killed the fish in question. Though I hasted to add CFCs report of a Macrobrachium rosenbergi killing and eating a catfish doesn't surprise me in the least, as that shrimp has a singularly bad reputation.

As that picture of a giant shrimp shows, the big ones are quite cool. Space and filtration requirements wouldn't be steep, so even if this shrimp carries on to grow, it'll be a fun pet in a single-species tank, perhaps?

Cheers,

Neale

Macrobrachium rosenbergi can take prey larger than itself...

 

[Flumpus]

Just a quick little update... I've been watching closely, and as a result the shrimp will be coming out of the tank as soon as I can figure out what to do with it. I've seen it challenge the gobies several times when they get too close, and while I don't think it could actually do much harm right now, I dn't want to risk anything as it gets bigger. I really don't want to just dispose of the shrimp, so I need to figure out something to do with it. I might end up with a tiny little brackish tank for it, since it seems to be enjoying the brackish conditions now. We'll see.

On a side note, all my gobies are sissies, and they swim away scared anytime the shrimp shows it's claws

 

[Flumpus]

The shrimp is gone! I thought it was dead a few days ago, but it showed up even bigger and meaner yesterday. He must have known it was Christmas, and he wanted holiday bloodworms like all my other fish. So this morning I went after him with two nets. I tried putting bloodworms in the net, but my gobies kept eating them. So then I took out all the plants, took out a rock that formed a cave where he likes to hide, and got after it. It didn't take long, but he was a fiesty little shrimp! After I caught him I threw him in a little tiny critter cage (I think that's what it's called) where I was keeping shrimp for the puffer. I put a little bit of crushed coral, a little salt, and in he went. I'll post some good pictures of him later after the water clears up. I don't know what I'm gonna do with him, other than just observe and see how long I can keep him alive