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title: "Scuds (Freshwater Amphipods): The Complete Culture & Live Food Guide" description: "Master scud culture (Hyalella/Gammarus): hard-water parameters, breeding a self-sustaining colony, harvesting, which fish love them, and the fish-egg predation warning." slug: scuds commonName: Scuds (Freshwater Amphipods) scientificName: Hyalella azteca family: Hyalellidae order: Amphipoda difficulty: Beginner minTankSize: 10 temperature: "16–26°C (60–78°F)" ph: "7.0–8.5" hardness: "8–25 dGH" lifespan: "~1 year" maxSize: "10 mm" origin: "North America; cosmopolitan in freshwater" publishedAt: "2026-06-04"

Scuds (Freshwater Amphipods): The Complete Culture & Live Food Guide

Scuds are one of the most useful and most underrated live foods in the freshwater hobby. These small, sideways-swimming crustaceans do two jobs at once: they are a protein-packed, carotenoid-rich live food that larger fish, puffers, and axolotls find irresistible, and they are a tireless cleanup crew that shreds detritus and uneaten food. Best of all, a scud colony established in a planted culture is almost impossible to kill — they breed continuously, hide in moss and leaf litter, and rebound from heavy harvesting. For anyone keeping fish too big for daphnia, scuds are the "set and forget" live food that keeps producing for years.

This guide covers what scuds are, how to set up a self-sustaining culture, the hard-water and calcium requirements that make or break a colony, how to harvest them, and the one important warning every breeder needs to hear before adding them anywhere near eggs or fry.

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What Are Scuds?

Scuds are freshwater amphipods — crustaceans in the order Amphipoda, the same broad group as the marine "sand fleas" and the Gammarus often sold as a dried turtle food. The two genera most common in the hobby are Hyalella (smaller, ~5 mm) and Gammarus (larger, up to 15+ mm). Their bodies are laterally compressed — flattened side to side — which gives them their characteristic sideways, flicking swimming motion and their other common name, "sideswimmers."

In the wild, scuds inhabit oxygen-rich shallows thick with leaf litter, detritus, and submerged plants, where they graze biofilm and shred decaying organic matter. That ecology translates directly to the culture: give scuds plenty of plant cover, detritus to process, and well-oxygenated, mineral-rich water, and they thrive with almost no intervention.

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Why Culture Scuds?

Scuds bring a combination of benefits no other single culture matches:

• A nutrient-dense live food. High in protein and rich in carotenoids, scuds enhance fish colour and provide excellent enrichment — they are a natural prey item that triggers active hunting.
• A self-sustaining colony. Unlike daphnia or worm cultures that crash and need re-starting, an established scud colony in a planted tank simply persists, breeding continuously.
• A built-in cleanup crew. Scuds shred leftover food, detritus, and decaying plant matter, processing waste that would otherwise foul the tank.
• Nearly indestructible. Because they hide in substrate, moss, and leaf litter and breed constantly, a scud population is extraordinarily resilient — you can harvest heavily without crashing it.
• Perfect for bigger eaters. Where daphnia is too small for many fish, scuds are an ideal size for puffers, larger community fish, cichlids, and axolotls.

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Water Parameters — Hard Water Is Non-Negotiable

The single most important fact about culturing scuds is that they are crustaceans that must have hard, calcium-rich water to moult successfully. Every time a scud grows it sheds its exoskeleton and must harden a new one, which requires dissolved calcium. In soft, low-GH water, moults fail and the colony slowly dwindles and dies. This is the number-one reason scud cultures fail.

If your tap water is soft, add a cuttlebone, crushed coral, or a remineraliser to raise GH — and watch the colony transform. Hard-water keepers, by contrast, often find scuds the easiest live food they have ever cultured.

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Setting Up a Scud Culture

Scuds are cultured much like a low-maintenance shrimp tank — minus the precision.

Container. Anything from a 10-litre tub to a spare aquarium. More volume buffers conditions and supports a bigger harvestable population.

Water. Hard, dechlorinated, oxygenated water. Mature aquarium water is an excellent start.

Cover and structure. This is the key to a productive colony. Pack the culture with java moss, other hardy plants, and leaf litter (Indian almond, oak, or beech leaves). This gives scuds surface area to graze, hiding places to breed, and detritus to process. A bare culture produces far fewer scuds than a heavily planted one.

Substrate. Optional. A thin layer of fine gravel or sand gives scuds more to forage in, but many keepers run them bare-bottom with moss and leaves.

Aeration. A gentle sponge filter or air stone keeps oxygen high and the colony vigorous. Scuds dislike stagnant, low-oxygen water.

Seed and wait. Add your starter scuds and let the colony establish for several weeks before harvesting heavily. Once established, it self-sustains.

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Feeding the Colony

Scuds are detritivores and omnivores that largely feed themselves in a planted, leaf-littered culture. To boost production for harvesting, supplement with:

• Blanched vegetables — spinach, zucchini, kale (a scud favourite).
• Fish flake or sinking pellets — a small amount the colony swarms.
• Leaf litter — both food and habitat; replenish as the leaves are consumed.
• Algae and biofilm — which grow naturally in a lit culture.

Feed lightly and let the scuds clear it — like any culture, overfeeding fouls the water. A well-fed scud colony processes its own waste remarkably efficiently, which is part of what makes it so low-maintenance.

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Harvesting Scuds

Because scuds hide in moss and substrate, harvesting takes a slightly different approach than netting daphnia from open water:

• Net the moss. Lift a clump of java moss and shake or rinse it in a container of water — scuds dislodge in numbers.
• Bait trap. Drop in a piece of vegetable or a sinking pellet; scuds swarm it, and you can scoop the whole cluster.
• Turkey baster. For targeted harvesting, suck up scuds where they congregate on food.
• Substrate disturbance. Gently stirring the substrate drives scuds into the water column where they can be netted.

Harvest as heavily as you like — an established colony shrugs it off and rebounds within days.

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The Critical Warning: Scuds and Eggs/Fry

Scuds are opportunistic omnivores, and a large scud will scavenge anything it can overpower. In practice this means: never introduce scuds into a tank containing fish eggs, freshly hatched fry, or a shrimp-breeding colony you want to protect. Large scuds will pick at eggs, eat newly hatched fry, and harass moulting shrimp and tiny shrimplets. They cannot catch healthy adult fish or adult shrimp, but vulnerable life stages are at genuine risk.

The right mental model is that scuds are a culture and a food, not a community-tank cleanup crew for breeding setups. Keep the colony in a dedicated culture, harvest from it, and feed the scuds to your fish — rather than housing scuds in the same tank where you are trying to raise babies. In a tank of robust adult fish with no breeding intentions, a resident scud population is a useful and harmless cleanup crew.

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Which Fish Love Scuds?

Scuds are an ideal-sized live food for fish that find daphnia too small:

• Pea puffers and other puffers — scuds provide both protein and hard chitin that helps wear down their ever-growing beak.
• Axolotls — an excellent enrichment food that triggers natural hunting and adds variety to an earthworm staple.
• Oscar fish, cichlids, and other large community fish — a substantial, nutritious live mouthful.
• Goldfish — relish scuds and benefit from the natural foraging.
• Larger tetras, barbs, and rainbowfish — chase them readily.

The carotenoids in scuds are a natural colour enhancer, so a few weeks of scud feeding visibly deepens reds and oranges in many fish.

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Troubleshooting

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Interesting Facts

• Scuds carry their young. Females hold eggs and developing young in a ventral brood pouch (a marsupium) until they hatch as miniature adults — there is no larval stage, so the colony grows fast.
• They are a wild bioindicator. Hyalella azteca is used in scientific water-quality testing because it is sensitive to pollutants — a healthy scud colony is a sign of clean, well-oxygenated water.
• "Sideswimmers" earned the name honestly. Their flattened bodies make them swim on their sides in a distinctive flicking motion, unlike the upright swimming of most aquatic animals.
• They are nearly immortal as a colony. Between continuous breeding, substrate hiding, and resilience to harvesting, an established scud culture can persist for years with minimal care.

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Bringing It Together

Scuds are the live food for everyone whose fish have outgrown daphnia. Set up a hard-water culture packed with java moss and leaf litter, keep the GH high so the colony can moult, feed lightly, and harvest by shaking the moss or baiting them with a vegetable — and you will have a self-sustaining supply of nutrient-dense live food that also keeps the culture clean. Respect the one rule — keep them away from eggs and fry — and scuds become one of the most reliable, lowest-effort cultures in the entire fishroom, ideal for puffers, axolotls, cichlids, and any fish that appreciates a substantial living mouthful.