Aquafeed Additives: Fish and Shrimp Feed Additives from Attractants to Astaxanthin

Aquafeed additives are feed additives in the sense of Regulation (EC) No 1831/2003 that go into extruded or pelleted feed for farmed fish and crustaceans, and each EU entry names the aquatic species it covers in its own words. That wording decides use: astaxanthin 2a161j names fish and crustaceans, while phytase 4a19 names fin fish only.

Aquafeed additives do five jobs: pigmentation, nutrient completeness for carnivorous species (taurine, histidine, vitamin D), digestibility (phytase), feed stability (binders, antioxidants) and health support (probiotics, immunostimulants). They span the EU types of feed additives, and their limits differ by jurisdiction: the EU caps astaxanthin at 100 mg/kg complete feed with all carotenoids counted, while 21 CFR 73.35 caps it in salmonid feed at 80 mg/kg (72 g/ton).

Every value is compiled from the EU authorising acts, the EU Register of Feed Additives, the eCFR and named peer-reviewed studies, checked on 3 November 2026; see the methodology.

What Shapes Aquafeed Additive Choice?#

Three things shape aquafeed additive choice more than on land: the feed is extruded and then sits in water, plant materials replace fishmeal, and EU authorisations word their aquatic species differently from act to act.

Extrusion, pellet water stability and nutrient losses#

Extrusion is the main loss point for heat-sensitive additives: vitamins A, E, C, B1 and folic acid are the most extrusion-sensitive, while B2, B6, B12, niacin, calcium pantothenate and biotin are stable (Riaz and colleagues, 2009).

Water stability is the second test: binder selection for aquafeed turns to celluloses, gums and alginates. Overages and coated forms for the sensitive vitamins are covered under vitamin stability in feed.

Fishmeal replacement and plant-rich diets#

When plant materials replace fishmeal in feed for marine carnivores, three additive needs rise: taurine, possibly histidine, and phytase to release phytate phosphorus.

Feeding stimulants raise intake through chemosensory stimulation and matter more as fishmeal falls, yet most active ingredients are feed materials. Dimethyl-beta-propiothetin has no EU register entry found.

EU species wording: fish, salmonids, finfish and crustaceans#

EU acts do not use one aquatic category: they name "fish", "salmonids", "salmon, trout", "other fin fish", "carnivorous finfish", "other aquatic carnivorous species, except mammals" or "crustaceans", and an entry covers only the animals its annex names. Taurine shows how wording moves: the old entry said "fish", and Implementing Regulation (EU) 2026/1859 of 29 July 2026 now names carnivorous finfish and other aquatic carnivorous species, except mammals.

From 16 December 2026, Implementing Regulation (EU) 2026/1115 lists salmonids (salmon, trout) among the major species used across feed additives by species dossiers. It sets salmonid efficacy studies at 84 days and salmon and trout tolerance trials at 90 days or until body weight doubles.

Aquafeed Additive Programme by Production Phase and Function#

The programme below lists the additive pages an aquafeed formulation draws on, grouped by function, with the EU entry, species wording and limit next to the US status; the phase column names a phase only where a dated trial or authorisation records one.

Minimum contents are legal minima, not recommended doses; no EU act sets a phase-specific aquafeed level for these entries.

The child pages below apply these entries to shrimp, salmonids and feeding stimulants.

Additives by Production Problem in Fish and Shrimp Farming#

Five production problems account for most aquafeed additive decisions: fillet and shell colour, phosphorus in plant-rich feed, nutrient gaps of carnivorous species, immune support and the physical and oxidative stability of the pellet.

Fillet and shell colour#

In the EU, astaxanthin 2a161j may be fed to fish and crustaceans up to 100 mg/kg complete feed (12 % moisture) counting every carotenoid source together, while the US caps astaxanthin in salmonid feed at 80 mg/kg (72 g/ton) under 21 CFR 73.35. The US total also covers astaxanthin dimethyldisuccinate, Paracoccus, Phaffia and Haematococcus pigments (21 CFR 73.37, 73.352, 73.355, 73.185).

ADMS 2a165 counts 1.38 mg as 1 mg astaxanthin. Canthaxanthin 2a161g names ornamental fish only, its salmon and trout use having been withdrawn by Implementing Regulation (EU) 2017/1145. Phaffia rhodozyma ATCC SD-5340 was denied by Implementing Regulation (EU) 2024/752, and Haematococcus pluvialis has no EU feed additive authorisation. The five sources are compared under astaxanthin sources for salmon feed.

Phosphorus release from plant-rich diets#

Three EU phytase entries name fish, each with a legal minimum activity rather than a dose: 4a19 for salmonids, ornamental fish and other fin fish, 4a16 for fish and 4a48 for all fin fish. The three entries are listed below.

• 4a19, AB Enzymes Finland Oy: salmonids and ornamental fish at least 500 FTU/kg, other fin fish at least 2 500 FTU/kg; Implementing Regulation (EU) 2025/142, runs to 2035-02-19.
• 4a16, Huvepharma EOOD: fish at least 500 OTU/kg; Implementing Regulation (EU) 2017/2274, runs to 2027-12-29.
• 4a48, Novozymes A/S: all fin fish at least 1 000 FYT/kg; Implementing Regulation (EU) 2024/2177, runs to 2034-09-23.

FTU, OTU and FYT are defined by their own acts and are not converted into one another. The 4a19 unit is measured at 37 °C and pH 5.5 (EN ISO 30024), and 4a19 does not cover crustaceans.

Nutrient gaps in carnivorous species#

Taurine is the clearest nutrient gap of carnivorous finfish: Implementing Regulation (EU) 2026/1859 sets a maximum of 25 000 mg/kg complete feed (12 % moisture) for carnivorous finfish and other aquatic carnivorous species, except mammals. In trials, Davis and colleagues (2021, Aquaculture) put the requirement of juvenile white seabass at 1.18 % of the diet over 70 days, and Salze and colleagues (2019, Aquaculture) found larvae from yellowtail broodstock fed 2.67 % taurine 53 % more likely to survive to first feeding. Histidine has EU entries for all animal species: 3c352, 3c352i, 3c353 and 3c354.

Vitamin D3 3a671 allows 60 000 IU/kg for salmonids but 3 000 IU/kg for other fish species, and 25-OH-D3 3a670a allows 0.800 mg/kg for salmonids against 0.075 mg/kg for other finfish and ornamental fish. Inositol 3a900 has no maximum and names finfish and crustaceans only.

Immunostimulants in aquaculture#

Immunostimulants have no EU feed additive status of their own: yeast beta-glucans have no EU additive authorisation and are sold as feed materials, and the only probiotic entry for food fish, Pediococcus acidilactici CNCM I-4622 (4d1712), is authorised to favourably affect growth. Ribonucleotide salts (2b) carry a recommended maximum of 50 mg/kg, not a legal maximum.

Evidence comes from single trials: Sajeevan and colleagues (2009, Aquaculture 287:248-252) found glucan dose and feeding frequency critical for immunostimulation in Indian white shrimp. Castex and colleagues (2021, Animals 11:3451) fed P. acidilactici (strain MA18/5M) to Litopenaeus stylirostris on restricted rations and recorded relative daily growth of 0.61 against 0.45 % body weight per day and 35 % higher gross feed conversion efficiency. Pond and water probiotics used for bioremediation are not feed additives; only feed-applied strains are in the register.

Pellet stability and fat oxidation#

Pellet binders and antioxidants keep aquafeed intact in water and its fat from oxidising, and their limits differ sharply between the EU and the US: lignosulphonate 1g565 is capped at 8 000 mg/kg for fish in the EU, lignin sulfonates at 4 % of finished pellets in the US. Urea-formaldehyde and sodium polyacrylate binders have no 21 CFR 573 listing and no EU authorisation found.

Propyl gallate 1b310 allows 40 mg/kg for salmonids and minor fin fish and 100 mg/kg for ornamental fish, while US GRAS status under 21 CFR 582.3660 limits total antioxidants to 0.02 % of the fat. Ethoxyquin is denied in the EU by Implementing Regulation (EU) 2022/1375, including for fishmeal stabilisation, yet 21 CFR 573.380 allows 150 ppm in fish food.

EU and US Rules for Aquafeed Additives#

An aquafeed additive is legal in the EU only for the species its implementing regulation names, at the maximum or minimum that act sets, while US status depends on the section of 21 CFR that lists the substance, and one never implies the other. Authorisation, renewal and labelling are explained under EU feed additive regulation.

Which EU entries name fin fish and which name crustaceans#

Crustaceans are named in the astaxanthin, ADMS, Pediococcus acidilactici, inositol and copper entries and, since 2026, in the taurine entry as "other aquatic carnivorous species, except mammals", while the fish phytase 4a19 and chromium 4d30 entries name fin fish only.

The table compares the fin fish and crustacean wording of each EU entry used in aquafeed.

Species wording as written in each act; "not named" means the act does not list crustaceans.

Entries past their printed expiry#

Several pigment and vitamin entries used in aquafeed have passed their printed expiry without a renewal act: astaxanthin 2a161j (printed expiry 2025-09-10), canthaxanthin 2a161g (2025-09-23) and vitamin C 3a300, 3a311 and 3a312 (2025-07-23). For each, the EU Register records a renewal application and still lists the entry pending the Commission decision (Article 14 of Regulation (EC) No 1831/2003), and no renewal act was found as of 3 November 2026.

The same wording applies to Paracoccus 2a(ii)167 (printed expiry 2018-08-15), betaine 3a920 and 3a925 (2025-07-23), B. velezensis 4b1820 for ornamental fish (2026-06-29) and zinc oxide 3b603 (2026-07-27). DL-methionyl-DL-methionine 3c306 for fish and crustaceans rests on Implementing Regulation (EU) 2015/1408, with a printed expiry of 2025-09-09.

US status: colour additives, food additives and GRAS#

In the US, aquafeed pigments are colour additives exempt from certification under 21 CFR 73, preservatives and binders are food additives under 21 CFR 573, and most vitamins are GRAS under 21 CFR 582. The three routes are explained under US feed additive regulation. Four sections matter most for aquafeed.

• 21 CFR 73.35 and 73.75: astaxanthin and canthaxanthin in salmonid feed, with all listed sources counted together.
• 21 CFR 573.380: ethoxyquin in animal feed and fish food.
• 21 CFR 573.600: lignin sulfonates as a pelleting aid.
• 21 CFR 582: GRAS vitamin D3 (582.5953), inositol (582.5370), vitamin C (582.5013) and histidine (582.5361).

Taurine under 21 CFR 573.980 covers growing chickens only, chromium under 573.302 cattle only, and 25-OH-D3 under 584.725 and 573.550 chickens and turkeys; phytase has no 21 CFR section and reaches the market through animal food GRAS notices.

Withdrawal periods, residue limits and the organic feed rule#

Astaxanthin 2a161j, ADMS 2a165, taurine 3a370, P. acidilactici 4d1712, phytase 4a19 and chromium 4d30 carry no withdrawal period in their EU acts; residue control appears as a maximum residue limit in the Paracoccus carotinifaciens entry, salmon 10 mg/kg and trout 8 mg/kg muscle. Sea lice treatments given in medicated feed are veterinary medicines, not feed additives.

Implementing Regulation (EU) 2021/1165 allows only one amino acid, fermentation-derived L-histidine monohydrochloride monohydrate for salmonids when the feed does not supply enough histidine; vitamins must come from agricultural products, else synthetic identical vitamins for aquaculture; and zootechnical additives are limited to enzymes and microorganisms. The full annex is under feed additives in organic production.

Sourcing Checklist for Aquafeed Additives#

Source an aquafeed additive in six checks, from the species wording of the act to the analytical method on the certificate.

1. Check that the act names the species: fin fish, salmonids or crustaceans.
2. Add up every carotenoid source against 100 mg/kg (EU) or 80 mg/kg (US).
3. Ask for the enzyme unit and its definition from the act.
4. Ask for heat and water stability data for extruded feed.
5. Ask for the analytical method: EN ISO 30024 for phytase, EN 15786 for Pediococcus, ion-exchange chromatography with visible detection or HPLC-FLD (AOAC 999.12) for taurine in feed.
6. Ask for FAMI-QS or GMP+ certification and the certificate of analysis for each lot.

Aquafeed Additive Questions#

Two questions about fish feed additives come up in formulation and buying. Size estimates for the whole sector sit on the feed additives market page.

Which feed additives are used in fish feed?#

Fish feed uses pigments (astaxanthin), nutrients for carnivores (taurine, histidine, vitamin D3, inositol), enzymes (phytase), probiotics, binders, antioxidants and preservatives, each within the species wording of its act. Typical EU entries are listed below.

• Pigment: astaxanthin 2a161j.
• Carnivore nutrients: taurine 3a370, histidine 3c352, vitamin D3 3a671, inositol 3a900.
• Enzyme: phytase 4a48.
• Probiotic: P. acidilactici 4d1712.
• Stability: lignosulphonate 1g565, propyl gallate 1b310, acetic acid 1a260.

What are functional feed additives in aquaculture feeds?#

"Functional feed" is a market term, not an EU legal category: in EU law the closest group is the zootechnical category, where Pediococcus acidilactici CNCM I-4622 favourably affects growth of fish and crustaceans, while immune-support ingredients such as yeast beta-glucans are feed materials. An additive claims only what its act states.