# Predatory Scuds Hunting My Baby Shrimp?!



## mordalphus (Jun 23, 2010)

By small invertebrates, I'm pretty sure they mean copepods and smaller.


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## 10gallonplanted (Oct 31, 2010)

A baby shrimp isnt really that much larger than a copepod, maybe twice the size but that isnt much. Just throwing out some possibilities. But in my opinion a scud is much too slow to catch a shrimplet that can shoot backwards super fast, but if the shrimp was used to the scuds it could be a different story.

Anyways, they will eat your moss for sure!


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## stevenjohn21 (May 23, 2012)

I had scuds in a tank over a year ago , since then I've had cichlids, crayfish and angelfish (not at the same time) I scooped up some of the substrate from that tank into a 10 gallon for my cherry shrimp and a week after setting it up I see scuds !!!! They are impossible to get rid of so I hope they are not killing the baby shrimp .


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## xenxes (Dec 22, 2011)

> The predatory ‘clumping’ behaviour of both species is described and shown to be a form of feeding frenzy upon congenerics. Clumping behaviour also results in significantly higher rates of congeneric predation on G. d. celticus females than on G. pulex females. Support is thus given to the hypothesis that differential predation by males on moulted females may be the primary mechanism by which the introduced G. pulex has displaced the native Irish species G. d. celticus.


That sounds like adult female scuds--after molt--the other species clump onto it and eat it? I haven't seen them eat moss though, just hide under my fissidens.









Looks like I have the g. pulex? Idk.

I just trapped ~100, turkey bastered out ~100, and probably have 1000 left...










Threw about 5 tubs of these out so far, they're still visible on the substrate swimming all over the place. AGHHHH. I guess they've always been around, but after removing my platies and habrosus they are much more active.


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## WestHaven (Jun 30, 2012)

How do they get into a tank in the first place?


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## xenxes (Dec 22, 2011)

I think mine came from a LFS, I thought it was a baby shrimp... stupid me. They carry/hatch eggs much the same way shrimp do.

Their mating is interesting.. I saw quite a few of them attached (one on the other's back)



> The shrimp will mate several times per year. During this process the male carries the female on his back as they are swimming. The female carries about 50 fertilized eggs in her egg pouch and these are orange in color and show through her semi-transparent body. The young shrimp hatch within the egg pouch and emerge as fully developed young shrimp but microscopic in size. The young develop an exo-skeleton but molt this a number of times as they increase in size. Sometimes these discarded exo-skeletons can be seen floating on the lake surface. Since the shrimp have no natural defense mechanisms, except camouflage, they usually hide in the Chara weeds and are more active during periods of low sunlight or after dark.


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## xenxes (Dec 22, 2011)

I left a bottle trap in last night and came out this morning to find everything inside but the scuds were dead, casualties: 7 sakura/pfrs, 1 cbs, 2 c. pygmaeus. I have tiny needle poked holes all over the top of the bottle trap so I don't think it's stagnant water.










I had previously trapped c. pygmaeus with rcs before for the same amount of time ~6hrs, and never had a casualty. Only difference is the hundreds of scuds. So they either (1) maliciously clawed the victims to shreds, or more likely they (2) scared/harassed them to death wiggling all over the bottle. 

(1) if we look at the anatomy, the first 2 gammarus species is capable of shredding into prey with its large gnathopods/claw









(2) whereas the pulex only has prehensile legs 









The ones that weren't mating were feasting on the corpses.

I'm not certain which species I have, the macro shot above was the best I have and the front pods are tucked in.

On a happier note, my filter box is blooming


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## Geniusdudekiran (Dec 6, 2010)

Darn you Xenxes, I was eating breakfast when I opened this thread. WAS. Lol


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## xenxes (Dec 22, 2011)

Lol sorry, I'm at war with scuds! Hope this doesn't lead to a tank tear down.

This is what I have. It looks much more vicious than the benign g. pulex. I'll post if I get a positive ID. Getting more and more suspicious this is the reason I have no baby shrimp in a large heavily planted well fed tank.


















Bottom pic is mine.

Perhaps even the common pulex is not as harmless as I thought, here a pic of one that _caught _a blood worm:


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## acitydweller (Dec 28, 2011)

yep. these are the guys i have in one of my tanks.

I was about to bridge my two 5.5 gallon tanks together but luckily i noticed these buggers before doing so. These guys are prolific breeders...

When these guys swarm, you better watch out. Hard to tell in the photo but were the legs and eyes missing on your sakura/pfr's?


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## xenxes (Dec 22, 2011)

Eyes weren't missing, but the fish was ripped open at the gut. I'm still have trouble believing they're capable... can't tell if they have claws or not from these pics. It almost seems like some do and some don't? Maybe I have 2 species.


























Wish I knew what species these are. Maybe instead of fighting it, I should just go from being a shrimp keeper to scud keeper. I mean, I still have hundreds. 

WTS: blue rili scuds $1 each. Lol.


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## EntoCraig (Jun 7, 2010)

Awesome Thread! I have scuds in my bucket ponds for the fish out back. I have always considered bringing some inside... I do keep terrestrial Isopods in my frog tanks.


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## hedge_fund (Jan 1, 2006)

people actually sell these on aquabid


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## hedge_fund (Jan 1, 2006)

...also, since you have so many scuds it's probably good if you run some experiments to see whether they actually do attack any tank inhabitants. maybe purposely injure a small shrimp and see if they go for it.....it's not cruel if it's in the name of science!


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## xenxes (Dec 22, 2011)

hedge_fund said:


> ...also, since you have so many scuds it's probably good if you run some experiments to see whether they actually do attack any tank inhabitants. maybe purposely injure a small shrimp and see if they go for it.....it's not cruel if it's in the name of science!


That's a good idea, not going to injure it though cause it'll just die. I'll see what happens with 1 shrimp and a swarm of scuds in a breeder box.


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## xenxes (Dec 22, 2011)

1 little cherry shrimp, 20 evil scuds, welcome to the Hunger Games - Shrimp Edition.


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## sayurasem (Jun 17, 2011)

xenxes said:


> That's a good idea, not going to injure it though cause it'll just die. I'll see what happens with 1 shrimp and a swarm of scuds in a breeder box.


The shrimp would probably die cause of heat. I have some of these guys in my tank.
I hate them, they look so scary and alien-ish. They do not prey on my baby shrimps... but they swim/ walk so freakin fast! All they do is bump into shrimps and scared the hell out of the shrimps...


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## xenxes (Dec 22, 2011)

sayurasem said:


> The shrimp would probably die cause of heat. I have some of these guys in my tank.
> I hate them, they look so scary and alien-ish. They do not prey on my baby shrimps... but they swim/ walk so freakin fast! All they do is bump into shrimps and scared the hell out of the shrimps...


Yea I think everything in the bottle trap was scared to death by the little crawlies. There's more room in the breeder box though, we'll see in 10 hours or so.


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## hedge_fund (Jan 1, 2006)

xenxes said:


> 1 little cherry shrimp, 20 evil scuds, welcome to the Hunger Games - Shrimp Edition.


Very nice. Perhaps you should rip off one or two legs from the baby shrimp to make it more interesting. I'm kidding...sorta.

Put a live bloodworm in there too and see if it disappears.


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## acitydweller (Dec 28, 2011)

You need to leave a bow and arrow in the breeder box then blow the horn!


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## AoxomoxoA (Apr 22, 2010)

What happened?!?

Edge of my seat... where's the eating popcorn smilie?:bounce:


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## 10gallonplanted (Oct 31, 2010)

Try putting a very young one in there too, like a baby.


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## acitydweller (Dec 28, 2011)

xenxes,, do you have a photo of your bottle trap? i have to build one of these


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## xenxes (Dec 22, 2011)

THIS JUST IN...

...Everything in the breeder box is *GONE* ... *POOF* disappeared like a sad magic trick. 










OH WAIT! ONE LONE SCUD IS ON ITS BACK, *TWITCHING* and *WRITHING* on the ground!










It can only mean one thing, an EPIC BATTLE ensued in the late of night, where the 20 scuds and 1 rcs attacked and cannibalized each other, until only ONE survivor remained!

...

that or everything fled and squeezed through the sides of the box. I'll need something more finely meshed to redo the experiment.


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## xenxes (Dec 22, 2011)

acitydweller said:


> xenxes,, do you have a photo of your bottle trap? i have to build one of these


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## acitydweller (Dec 28, 2011)

Thanks X. either you have some epic glass cutting skillz or you used a plastic coke bottle 

im going to opt for the later and see how that goes. im thinking to use a rubberband to keep the inverted top stationary while the bottle is laying on its side.


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## JoraaÑ (Jun 29, 2009)

If possible introduce 4-5 Endlers(must have a female) and see what happens in 3-5 days...Of course shrimplets will be eaten as well by them. Dont feed Fish before you put them in tank. A friend had a problem in his planted tank: this is how he got rid of them....where as he has another tank just for Scuds...to feed to cichlids.


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## jlieu (Jun 7, 2012)

Some African Cichlids would most certainly remove you of all your problems in no time...:icon_lol:

The Endlers trick may work as well. Plus their mouths are too small to really do any harm to adult shrimps (or even juvies IME).


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## diwu13 (Sep 20, 2011)

xenxes said:


> Eyes weren't missing, but the fish was ripped open at the gut. I'm still have trouble believing they're capable... can't tell if they have claws or not from these pics. It almost seems like some do and some don't? Maybe I have 2 species.


I think they do have huge claws. It's that ball thing under the stomach I believe.

And that's funny. Experiment gone wrong lol. I'm pretty sure they all ate each other until none remained except that lone victor. And he's so full from eating all the other inhabitants he's laying on his back.


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## Jadenlea (Sep 15, 2011)

I am confused.. how can everything be gone? Shrimp couldnt kill and eat 20 scuds


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## AoxomoxoA (Apr 22, 2010)

xenxes said:


> It can only mean one thing, an EPIC BATTLE ensued in the late of night, where the 20 scuds and 1 rcs attacked and cannibalized each other, until only ONE survivor remained!





diwu13 said:


> I'm pretty sure they all ate each other until none remained except that lone victor. And he's so full from eating all the other inhabitants he's laying on his back.


Definitely this one:thumbsup:


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## randyl (Feb 1, 2012)

I think they all went back to the main tank. These breeder boxes need serious mod to prevent this.


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## diwu13 (Sep 20, 2011)

Jadenlea said:


> I am confused.. how can everything be gone? Shrimp couldnt kill and eat 20 scuds


No this is very possible. I have zero scuds in all my shrimp tanks because each shrimp can eat 20+ scuds @[email protected]!!


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## WestHaven (Jun 30, 2012)

This is so interesting. Are there any benefits of having scuds in your tank?


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## xenxes (Dec 22, 2011)

Scuds are actually a sign of good health in a tank. They are fairly sensitive and only exist in very clean and oxygenated water. They are mainly detrivores that feed off waste in the top inch of the substrate. Great for any fish tank, but they're competing with, and perhaps eating my shrimp! More evil experiments when I get back home. Out of town for a few.


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## sayurasem (Jun 17, 2011)

xenxes said:


> Scuds are actually a sign of good health in a tank. They are fairly sensitive and only exist in very clean and oxygenated water. They are mainly detrivores that feed off waste in the top inch of the substrate. Great for any fish tank, but they're competing with, and perhaps eating my shrimp! More evil experiments when I get back home. Out of town for a few.


They also eat moss. I notice they always hangout on my flame moss pad and some of my moss strands are "bald" missing leaves only the stems remains.


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## hedge_fund (Jan 1, 2006)

sayurasem said:


> They also eat moss. I notice they always hangout on my flame moss pad and some of my moss strands are "bald" missing leaves only the stems remains.


Yup, I can confirm this too about the flame moss.


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## WestHaven (Jun 30, 2012)

How could one get some scuds in your tank if you wanted to?


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## hedge_fund (Jan 1, 2006)

WestHaven said:


> How could one get some scuds in your tank if you wanted to?


You can come to Greenwich CT and pick some up from me for free.


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## WestHaven (Jun 30, 2012)

hedge_fund said:


> You can come to Greenwich CT and pick some up from me for free.


Ok, I'll do that sometime in the future. My tank is still cycling.


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## BlackDiamondShrimp (Feb 2, 2011)

Threadfin Rainbows are so effective in exterminating these scuds and so do the Least Guppies. I had 75Gallon planted tank where literally millions of scuds swam in open freely , every nook and cranny and root were infested with these guys. The 7 Threadfin Rainbows, 7 Least Guppies, and 5 Dwarf Cajun Crayfish eliminated them to extinction in less than 3 months. I was shocked actually. When I removed the tank of fish, shrimps, and crays the scuds never ever again returned this was 1 year ago.

Bullet Points:
The Threadfin Rainbows will actively and efficiently hunt the babies since their mouths are so small

The Least Guppies will eat babies and juvies very efficiently and actively, night and day non-stop. Seriously these guys don't know when to stop.
Least Guppies are very intelligent and will investigate constantly where the scuds are hiding, due to their curious nature unlike the regular guppy too dumb to find food unless it is waved at them.

The Dwarf Cajun Crays will hunt the adults in very nook and cranny they can crawl into(adult scuds too big for the Rainbows and Guppies)


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## shrimpNewbie (May 6, 2011)

If I had scuds I wouldn't want them gone I'm a fan of all
Life in a tank even nematodes. I hope someone local has scuds to seed my tank my RCs can't outbreeding my fishes hunger.


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## sayurasem (Jun 17, 2011)

shrimpNewbie said:


> If I had scuds I wouldn't want them gone I'm a fan of all
> Life in a tank even nematodes. I hope someone local has scuds to seed my tank my RCs can't outbreeding my fishes hunger.


Why put fish and shrimps together


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## xenxes (Dec 22, 2011)

I threw back in 2 platy fry/juvies (.5") in the tank, they active hunt through the gravel. Large reduction in scuds in the water column, but you can still see a few large ones swarming around. They'll probably eat some baby shrimp too but at this point the benefit outweighs the cons. Still have tons of scuds, most are just in hiding.

I've noticed that in my tanks with a fine sand substrate, there are very few scuds. They only see to borrow through gravel / fluval plant stratum.


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## xenxes (Dec 22, 2011)

The UG I added to my tank last night are ALL EATEN. But I think the CBS were the culprits. I woke up this morning to see about 10 of them swarming around the plant remnants.


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## xenxes (Dec 22, 2011)

Couple more shots for all you scud lovers, does it have claws? I still can't tell... note the compound eyes.


















And here's a platy baby hunting them!


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## hedge_fund (Jan 1, 2006)

I like this thread since it's dedicated to something that I hate. Keep the pics coming.


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## xenxes (Dec 22, 2011)

Lol.

An easy way to "fish" out scuds is to drop in a piece of blanched veggie, wait 10 mins then take it out. 

They're not quick like shrimp and usually can't all jump off. Caught maybe 40-50 scuds on a large piece of blanched eggplant this way last night.


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## xenxes (Dec 22, 2011)

Last set of pics I'm posting, I'm waiving the white flag  They win.









SCYTHE-like hooked claws!









More eggs!!









This one tried to attack me through the glass with a high pitched shriek!


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## pinoyghost2 (Feb 13, 2012)

I have them in my shrimp tanks too, and I noticed they are eating the algae off the tank glass which is also what baby shrimps need to survive in the first few weeks....this might be why we are seeing less and less baby shrimps surviving to adult/juvie stages....the scuds are eating their supplies!

I have only ever seen the scuds jumping over the shrimps not actually trying to grab them etc...so this is why I think the populations are decreasing in our tanks...the scuds are eating machines and LOVE anything green!

:angryfire


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## diwu13 (Sep 20, 2011)

Chances that some scuds hooked a ride into my moss tank with the shrimp?

If all my moss disappears over a course of a week I'll be very angry


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## xenxes (Dec 22, 2011)

They don't eat my moss (fissidens).

And I don't think your moss tank water is clean enough for them to survive


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## diwu13 (Sep 20, 2011)

Hey hey, I switched my moss tank water to RO/DI water now as well :X! So any chance they coulda came in with the shrimp?


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