Culturing scuds

Freshwater amphipods, AKA scuds, AKA sideswimmers, AKA gammarus, AKA baby shrimp, AKA ohgrosswhatisthat, are small crustaceans that are abundant in many aquatic habitats and form a major part of the diet of many small fishes. While they can swim, scuds tend to spend most of their time clinging to surfaces or wedged into interstitial spaces. They are grazers and detritivores that feed on a variety of decaying matter, aufwuchs, and biofilms.

Q. What do scuds look like?

A. Scuds are laterally compressed, vaguely shrimplike animals usually less than 3/4" in length. They have a characteristic C-shaped posture, and unlike shrimp and crayfish lack claws (chelae) and tail "fins" (uropods). When disturbed they swim in often circuitous routes but at a relatively steady speed, unlike the jerking flight of many crustaceans. They may be various shades of gray, brown, or pinkish.

Q. What are they good for?

A. Scuds are relished by numerous aquatic predators, including minnows, darters, killifish, juvenile sunfish, aquatic salamanders, and crayfish. They are also detritivores who can help keep your tank clean if they survive. They make great additions to planted tanks, refugia, and large filters.

Q. Where can I find scuds?

A. Scuds occur in both slack and flowing water environments of all sizes and everywhere from bottomland swamps to mountain brooks to cave pools. Scuds reach highest abundances where food and structure are both readily available. Examples include: leaf mats, dense tree roots, and thick submersed or floating vegetation. They can also be found in gravel and muck, but seem to be less concentrated in those habitats.

When I want large numbers of scuds, I go to a spring run I know that has dense mats of watercress, duckweed, and riccia. Holding a net immediately downstream of a the mat, I give it a vigorous shaking; this dislodges hundreds of scuds who then drift into my net.

Q. What do I need to culture scuds?

A. Not much. You need of course a container to house them, dechlorinated water, and food; in a small container you will also need some oxygenation. Containers as small as one gallon or even less may be used, but the water chemistry in these tiny containers is easily knocked off balance before you know it; I prefer to use 10 gallon containers or larger if at all possible. It is wise to maintain more than one colony in case one crashes or is overharvested and needs time to recover.

I do not use filtration in my colonies. Smaller containers are more likely to need filtration; if you decide to use filtration, a gentle air-driven system such as a sponge or undergravel filter is best; power filters are likely to suck in scuds and possibly mangle them or strand them in the filter chamber.

Water chemistry is not terribly important; hardness, pH, and so on matter little. Like all inverts, scuds are sensitive to copper. Room temperature is fine. I like to start a colony with scuds from several sources to try to ensure that at least one group will thrive in the conditions provided.

Q. What do I feed my scuds?

A. Scuds are catholic eaters; they like fish food, old filter sponges, dead and dying plants, vegetable scraps, and so on. They will even eat paper towels. A scud colony can act as a convenient waste disposal as well as a food source, though you must be careful not to foul the water by adding too much food. Also keep in mind that whatever the scuds eat your fish will eat at second hand, so keep it clean.

Q. Can I keep anything else in my scud colony?

A. Many other invertebrates will thrive in a scud tank, including daphnia and other cladocerans, copepods, isopods, and snails. My colony is periodically invaded by midges. I have not tried raising blackworms, tubifex, or shrimp in a scud colony, so I can't say how successful that would be.

I hope this was helpful. If anyone else with scud experience would like to add to this, please feel free.

Thank you, that was very enlightening. I appreciate it very much.

I hope this was helpful. If anyone else with scud experience would like to add to this, please feel free.

Newt, thank you VERY much. I keep scuds in a 3 gallon jar with a few aquatic plants and soil/sand. They have quite the appetite. They don't play well with small Sphaeriidae though. This morning I noticed a few scuds picking at what was left of an open shell. The pill/nut clam seemed to be doing well for months, shifting around the substrate and whatnot.

Edited by topminnow, 07 July 2008 - 06:15 PM.

Hey Nate, wanna send me a few hundred skuds? That information was very helpful!

-Nate

Nice job!
I've had good luck inadvertently culturing scuds in the canister of good sized canister filters. Never planned it that way but it's happened on multiple occasions. Canisters with scuds [or snails] thriving in them don't need to be cleaned. The flow may go way down, somewhat limiting bio filtration, but the trade off is fast reduction of solid waste and steady supply of live food.

I have a scud culture going, its in a 20 gallon "keg" bin. There is about an inch of sandy gravel, land then 6 inches or so of leaves and sticks. It just has a single airstone. I feed them old flake food occassionally but they basically take care of themselves. I started with less than a hundred now it is self sustaining.

Edited by scottefontay, 08 July 2008 - 06:57 AM.

Scott- that sounds like a nice setup. I leave my scud tanks bare bottom for ease of maintenance and collection, but they would probably do better with more structure. I accidentally introduced some duckweed to my big colony, and it got out of hand; the scuds loved it though. I finally ended up scooping out a gallon of mixed Lemnaceae and most of my scuds; they're in the freezer now, and will ultimately be turned into gelatin-based fish food.

Mike- I've been trying to get scuds established in the bioball-filled filter chamber in the back of my big tank, but they haven't really taken off yet. The physids are doing quite well, though.

Nate- I'll be happy to send you some scuds, but I suggest trying to find your own first. They shouldn't be too hard to find!

Topminnow- I was wondering why my sphaeriids never lived long; it never occurred to me that the scuds might be attacking them! Of course, the scuds may be scavenging rather than predating.

Mander- no problem. Your name suggests that you're a salamander fan; if you're raising larvae scuds are a great food once the larvae have gotten big enough to eat them. At a certain size it becomes difficult to keep them happy on daphnia alone.

Mander- no problem. Your name suggests that you're a salamander fan; if you're raising larvae scuds are a great food once the larvae have gotten big enough to eat them. At a certain size it becomes difficult to keep them happy on daphnia alone.

Yes, I love salamanders, as I'm sure you do, too. We have plenty out in the woods, but none in the tank. Might try to find some for the pond. Hubby isn't a pet person, he doesn't like to see things caged. So far, he's okay with fish. Salamanders might be a stretch for him. We'll see.

Part of me wants to do the nurturing thing and raise quality food for my "babies." Part of me has been a short order cook for 22 years (ie MOM) and knows full well what it's like for one to want pancakes while another wants steak; if one goes grocery shopping, the entire family will leave to parts unknown for days at a time, if one doesn't shop, hungry wolves will knock down the door and you have ten seconds to produce food before they start gnawing the furniture. I want to do the culture thing, but I don't know if I could handle one more thing to feed!

That's the great thing bout scuds- they're largely self-sufficient. Just feed them whenever you think about it; they'll be fine between times, especially if you add a few fast-growing plants and some dead leaves or bits of wood to the tank. I've literally gone months without feeding my scuds; production slows down a bit, but that's not a problem when all my larvae have grown up and I don't need as many scuds for food.

I want to do the culture thing, but I don't know if I could handle one more thing to feed!

Mander, the culture I described I think I have fed three times since early spring and that was only a pinch or two of old flake food. It gets neglected for sure but there are always young present. I don't harvest it heavily though.

Newt, This method is a bit messy, but is working rather well. I put a net full of the detritus in a shallow tupperware container and slowly lower it to the bottom of my Iowa darter tank They forage. Its the only thing that seems to fill their bellies. I do that once or twice a week on top of frozen brine and bloodworms for those guys. I have thought in the past that putting a big net-bag full of detritus with scuds into a tank would be a good "hands-off" live food feeder.


I tried doing the cherry shrimp-type thing with my fry tanks (putting a couple cherry shimp in to help clean-up, ending with lots of cherries), but the scuds never seemed to take off like the cherry shrimp do in those conditions.

Edited by scottefontay, 08 July 2008 - 12:19 PM.

Topminnow- I was wondering why my sphaeriids never lived long; it never occurred to me that the scuds might be attacking them! Of course, the scuds may be scavenging rather than predating.

Yes, I figured they were scavenging but are they exhausting preferred food source? The tubifex seem to be disappearing as well. Im scared to check how many individuals are in the substrate. I haven’t been feeding, just observing. The scuds seem to have eaten the cyclops but nematodes and several dozen daphnia still remain. Luckily I have a container next door with a steadily growing cyclops culture.

Can you just add scuds straight to a tank with fish or will the fish eat them all before they establish (planted tank)?

Can you just add scuds straight to a tank with fish or will the fish eat them all before they establish (planted tank)?

Gambusia, it depends on what 'fish' you're speaking of but yes it's possible to add scuds to an esablished aquarium without fish eating them.

Gotcha.

I was thinking small minnows

If you want the scuds, blackworms, or any other live food you add to a tank to try and become established as topminnow said, it depends on the fish, but I have found that adding the critters at night or lights-out helps get them to the bottom. There is a reason paratroopers drop at night, after all . Also, scuds will need some cover.

I've been amazed at the number of times I've pulled up a clump of plants from a tank and found scuds living on it when none had beed added for months. In thickly planted tanks, especially the kind [like mine] where the mulm gets inches deep, they survive surpisingly well.
I doubt they'd get established if mudminnows are present though. My mudminnows get so EXTRA excited by the sight of a scud, it's clear scuds are a staple or prefered food item.
It's cool to add a bunch of scud at night as [suggested above] and watch the mudminnows go into hunt mode the next morning when they spot the first scud.

Can a scud colony be kept in the dark or do the need natural light?

Very nice article. I have been thinking of doing a scud culture for my fish. When I bring scud home to my fish, they rarely reach the tank bottom before the minnows get them. I often use a large turkey baster to feed the darters. I LOVE watching the darters grab a scub and bash it into the rocks to kill it.

If you have a colony going, how often can it scud be removed for food? I know that it depends on how many you have, but is there a minimun level that should be maintained?

So that's what those things are. I have a spring stream packed with them, and they're a real treat for my darters. That little stream also has some of the largest banded sculpin I've ever seen. They must get fat and sassy eating scuds.

Haven't seen this for some years, but when I was a boy, I remember them migrating upstream. The shore of the creek would have a line of them, slowly working their way upstream. I used to build barriers just to watch them figure out how to get around.

Bart- They do fine in the dark.

Josh- There are too many factors there to give you any kind of definitive answer. I try to maintain several colonies; I harvest from one until the scuds seem scarce, then I rotate to another.

John- That is really interesting. I've never heard of scuds migrating like that- it sounds almost like the way spiny lobsters migrate.