Natural food & live-prey guide

Taxon: Artemia spp. instar I

Size fit: ~0.5 mm newly hatched; first-feeding mouth-size varies

Culture: Hatch commercial cysts in a separately aerated saline vessel; rinse before offering

Harvest: Separate swimming nauplii from floating empty shells and unhatched cysts; feed small harvest promptly

Risks: Cyst-shell ingestion, salt transfer, batch pathogens/contaminants, freshwater survival is limited; not all newly hatched fry can ingest

Evidence: direct medaka study

Source 1 ↗ · Source 2 ↗

Taxon: Artemia spp. instar II/metanauplii

Size fit: larger than new instar I; size increases with age

Culture: Feed newly hatched Artemia suitable algae or a tested enrichment emulsion after they become feeding stages

Harvest: Rinse and offer live to size-appropriate fish; use quickly

Risks: Enrichment and holding lower batch simplicity; increased size may exclude fry; fatty acid results are other-species context

Evidence: aquaculture extrapolation

Source 1 ↗ · Source 2 ↗

Taxon: Artemia spp. adults

Size fit: much larger than nauplii

Culture: Raising beyond nauplii requires feeding and controlled saline culture

Harvest: Feed size-appropriate parts/individuals

Risks: Not a first-fry food; cannot persist indefinitely in freshwater

Evidence: aquaculture extrapolation

Source 1 ↗

Taxon: Moina spp. neonates

Size fit: young often <400 µm; size varies by species and culture

Culture: Separate gentle-aeration freshwater cultures with algae/yeast; ensure no copper/pesticides

Harvest: Harvest gently through fine mesh; select appropriately small prey; rinse

Risks: Hard to grade neonates; contamination with Hydra/insect predators; manure or polluted inoculum risks

Evidence: fish aquaculture extension

Source 1 ↗ · Source 2 ↗

Taxon: Moina spp. adults

Size fit: ~700–1000 µm adults per UF/IFAS

Culture: As above; replicate cultures for continuity; 24–31 °C optimal culture guidance (species/conditions vary)

Harvest: Harvest no more than 20–25% per day in established semi-continuous culture per IFAS; rinse

Risks: Too large for tiny fry; high density may stress fish; culture crashes and predators

Evidence: fish aquaculture extension

Source 1 ↗ · Source 2 ↗

Taxon: Daphnia spp. neonates

Size fit: much smaller than adults; species-specific; no universal size listed

Culture: Culture clean freshwater Daphnia on microalgae/yeast appropriate to strain

Harvest: Harvest small prey carefully; rinse with clean water

Risks: Particle/prey size and tank access; cultures can carry planaria/hydra or other organisms

Evidence: broader freshwater aquaculture

Source 1 ↗ · Source 2 ↗

Taxon: Daphnia spp. adults

Size fit: species-dependent, often larger than adult Moina; not a first food

Culture: Culture with clean water and algae/yeast; shade appropriately

Harvest: Rinse and distribute modest quantities

Risks: Adults can be too large; live cultures may transport other organisms

Evidence: breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Paramecium spp.

Size fit: microscopic but species/mouth-size dependent; no single universal number

Culture: Starter culture grown with bacterial/yeast support in separate jar; maintained and replicated

Harvest: Use pipette after letting heavy debris settle; deliver small cloud of paramecia, not sour/rotting culture substrate

Risks: Overfeeding bacteria/rot; GEX explicitly cautions some are too large immediately at hatch and excessive survivors can stress fry

Evidence: medaka manufacturer and breeder guidance

Source 1 ↗ · Source 2 ↗

Taxon: Brachionus calyciflorus and other appropriate freshwater rotifers

Size fit: typically very small; validate culture species and actual body dimension

Culture: Separate algae-fed culture, screen for other plankton

Harvest: Harvest with appropriate plankton mesh, rinse and dose lightly

Risks: Nutrient quality depends on algae/enrichment; predatory contamination; many papers use zebrafish or other fishes, not medaka

Evidence: other fish controlled study

Source 1 ↗ · Source 2 ↗

Taxon: Mixed ciliates/other protozoans, rotifers, micro-zooplankton

Size fit: highly variable, not a single organism/size class

Culture: Culture separate filtered/conditioned microfauna and verify microscopically if possible

Harvest: Use small clear-water aliquots; avoid decaying vegetable mass into fry tanks

Risks: Undefined composition, possible predatory organisms, water fouling and unstable yields

Evidence: medaka husbandry practice

Source 1 ↗ · Source 2 ↗

Taxon: Small free-living freshwater Copepoda nauplii

Size fit: variable across copepod species and instars; check under magnification

Culture: Isolated culture of verified non-predatory species with microalgal/microfaunal feed

Harvest: Sieve by size and rinse; screen out adults

Risks: Some adult cyclopoids prey on fry/eggs; wild cultures introduce predators

Evidence: broader aquaculture extrapolation

Source 1 ↗ · Source 2 ↗

Taxon: Mixed suspended algae and associated plankton

Size fit: particle and microbial size varies

Culture: Grow well-identified greenwater separately under light; protect from outdoor contaminants

Harvest: Use controlled aliquots or maintain stable greenwater fry container, never assume chlorophyll means complete balanced diet

Risks: Bloom crash, nighttime oxygen demand, pH swings, cyanobacteria and contamination; not a guaranteed complete food

Evidence: medaka breeder and manufacturer guidance

Source 1 ↗ · Source 2 ↗

Taxon: Bacteria, protozoa, algae and metazoan microprey

Size fit: variable living film, microfauna not characterized

Culture: Maintain mature safe aquarium surfaces/plants without chemical exposure

Harvest: Allow natural grazing; monitor feeding/condition to avoid starvation

Risks: Biofilm alone is not nutritionally quantified or a complete feeding plan; pathogen/predator hitchhikers

Evidence: husbandry inference

Source 1 ↗ · Source 2 ↗

Taxon: Panagrellus redivivus

Size fit: typically slender <2 mm length; width more relevant to swallowing

Culture: Small oats/yeast culture in lidded ventilated container

Harvest: Lift worms from clean container sides and rinse; avoid transferring culture paste

Risks: Sinking behavior may limit surface-feeding access; culture contamination and fouling

Evidence: aquarist breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Panagrellus spp. marketed as banana worms

Size fit: thin and small; exact species and size vary

Culture: Maintain separate culture, identify stock; avoid treating trade name as species

Harvest: Harvest and rinse off sidewall

Risks: Too much growth medium fouls fry water; exact taxon size unknown

Evidence: aquarist breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Panagrellus spp. trade strain

Size fit: thin; confirm culture starter identity

Culture: Culture similarly to microworms

Harvest: Harvest in clean water by pipette

Risks: Commercial culture identity and dimensions may be ambiguous; avoid proven-benefit claims

Evidence: candidate context only

Source 1 ↗

Taxon: Turbatrix aceti

Size fit: approx 1–2 mm length but narrow body; site-dependent

Culture: Cultured in dilute cider-vinegar water and apple; ventilate culture

Harvest: Separate live worms from vinegar through clean water/floss transfer; do not pour acidic culture into fish tank

Risks: Acid transfer changes pH; contamination/fermentation; no controlled medaka advantage

Evidence: aquarist breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Enchytraeus buchholzi (commonly marketed)

Size fit: too large for new fry; portions may be needed

Culture: Maintain damp foam or clean soil-free substrate with light feeding

Harvest: Rinse worms collected from glass/acrylic over substrate

Risks: Overfeeding, high-energy food, mites/mold and culture substrate contamination

Evidence: aquarist breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Enchytraeus albidus

Size fit: usually many mm to cm; too large for fry

Culture: Cultures need cool conditions, about 55–65 °F per breeder guide

Harvest: Harvest/clean; offer small portions

Risks: Heat sensitivity; fatty-food claims from aquarists not a proven medaka nutrient assay

Evidence: aquarist breeder practice

Source 1 ↗ · Source 2 ↗

Taxon: Chironomidae larvae (not marine Glycera)

Size fit: variable larvae size; typically too large for newly hatched fry

Culture: Buy traceable cultured/frozen product; do not culture in foul water

Harvest: Use hygienic small portions; frozen/thawed is not LIVE food

Risks: Allergen handling, environmental contamination in live material, decomposition of excess

Evidence: medaka breeder practice

Source 1 ↗

Taxon: Collembola

Size fit: small surface insects, species dependent

Culture: Isolated clean springtail culture away from pesticides

Harvest: Float small numbers on surface; monitor interest

Risks: No medaka controlled evidence; terrestrial culture contamination, unconsumed individuals

Evidence: candidate context only

Source 1 ↗

Taxon: Drosophila melanogaster/other cultured drosophilids

Size fit: small flies, too large for fry

Culture: Clean flightless culture in closed container

Harvest: Feed few at surface without adding media

Risks: Escape/pest issues; limited direct medaka diet evidence

Evidence: candidate context only

Source 1 ↗

Taxon: Copepoda incl. cyclopoid/calanoid species

Size fit: larger than their nauplii; variable

Culture: Maintain verified cultured species; avoid unknown wild plankton

Harvest: Provide only confirmed safe small species

Risks: Predatory copepods may attack fry; not a blanket first-food recommendation

Evidence: candidate context only

Source 1 ↗ · Source 2 ↗

Taxon: Lumbriculus variegatus

Size fit: long thin aquatic worms; adult portions only

Culture: Prefer reputable cultivated stock, clean cool oxygenated holding water

Harvest: Rinse carefully and offer limited pieces

Risks: Possible pathogen or parasite contamination from wastewater cultures; not for fry

Evidence: aquarist breeder practice with risk

Source 1 ↗ · Source 2 ↗

Taxon: Tubifex spp.

Size fit: long thin aquatic worms; adult portions only

Culture: Avoid wild wastewater-grown cultures; prefer safer cultured alternatives

Harvest: If offered, controlled-source material only, rinse thoroughly

Risks: High contamination risk in organic waste/sludge environments; pathogen concern

Evidence: high risk breeder context

Source 1 ↗ · Source 2 ↗

Taxon: Culicidae larvae

Size fit: larvae sizes vary; first instars small

Culture: DO NOT intentionally breed mosquitoes in open containers

Harvest: If naturally present in stocked tanks remove/consume before emergence but do not cultivate

Risks: Public-health vector hazard, larval escape and adult mosquito production, contaminants

Evidence: environmental hazard context

Source 1 ↗ · Source 2 ↗

Taxon: Ostracoda

Size fit: variable hard-shelled microcrustaceans

Culture: Typically hitchhikers in established planted systems; controlled culture identity difficult

Harvest: Offer only known-safe size/stock

Risks: Hard valves, unknown species, hitchhiker contaminants; no controlled medaka growth proof

Evidence: candidate context only

Source 1 ↗

Taxon: Amphipoda e.g. Hyalella/Gammarus

Size fit: species and age vary; many too large

Culture: Cultured in separate leaf litter/planted tub

Harvest: Offer small juveniles only when fish demonstrably ingest them

Risks: Can become tank hitchhikers; competition or plant grazing; no controlled medaka benefit shown

Evidence: candidate context only

Source 1 ↗