If you put commercial aquafeed under a microscope, you might find plastic fibres, by the thousand per kilogram. And those fibres are made of the same polymers as the sack they came in.
Siddique et al. (2025) analysed 17 commercial tilapia feeds sold in Bangladesh. Every sample was contaminated, averaging 1,150 ± 391 microplastics per kilogram and peaking at 2,150 MPs/kg in a grower feed. Fibres were about 85% of the haul, and most particles sat in the 100–1500 µm range, small enough to go down with the pellet unnoticed.
This is not one bad batch in one country. Gündoğdu et al. (2021) sampled fishmeal from 26 producers across 11 countries and found loads from zero up to 526.7 particles per kilogram. The contamination travels with the ingredient.
Two Dominant Polymers
The two dominant polymers in those tilapia feeds were polypropylene (up to 43%) and polyethylene (up to 34%). These are the exact materials aquafeed is packed in: woven PP sacks, BOPP lamination, PE liners, and the polypropylene rope used to stitch and stack them. Mohsen et al. (2024), sampling feed for five species in China, found the same pattern i.e. mostly microfibres, dominated by propylene, and concluded packaging and processing were the main sources.
Siddique et al. (2025) attribute the contamination to feed processing, packaging materials, and the ingredients themselves. Plastic bags and ropes fragment during grinding and handling, and the pieces end up in the mix.
Where The Plastic Gets In
| Entry point | Evidence/Source |
| Fishmeal and other raw ingredients | Directly measured across 11 countries. |
| Processing: grinding, drying, plastic machine parts | Grinding fragments plastic already present. |
| Packaging: woven PP sacks, BOPP lamination, liners, ropes | Named as a main source; polymers match. Not yet quantified alone. |
| Storage and handling on-farm | Plausible and fully within your control. |
Packaging is named as a main source and the polymer evidence lines up, but the exact share is still an open question. Anyone selling you a precise number for it is guessing.
How Yield Is Affected
Wang et al. (2024) pooled 3,757 biological endpoints from 85 laboratory studies and found microplastic exposure significantly inhibits fish growth, reduces survival and reproductive ability, and drives substantial oxidative damage.
The mechanism is unglamorous. Particles accumulate in the gut and create a false sense of fullness, so the animal eats less. They abrade the intestinal lining. Some reach the liver, triggering oxidative stress the fish must spend energy managing, energy that was supposed to become body weight. Each is a direct tax on feed conversion. Given that feed is 60–80% of tilapia production cost (Ragasa et al., 2022, as cited in Siddique et al., 2025), a quiet FCR penalty is the most expensive thing that can happen in a pond.
How TerraPHA Helps
TerraPHA Biotech, World’s first commercial non-GMO biopolymer company, produces polyhydroxyalkanoate (PHA) from naturally occurring, non-GMO microorganisms. PHA matters here for one reason as unlike PP and PE, microbes in soil and water metabolise it instead of leaving it to persist as a fibre. A fragment shed from a PHA-based material does not spend the next decade circulating through your pond and your fish.
TerraPHA works both sides of this as their biopolymers are built to break down instead of accumulate, and PHA-based inputs for aquaculture, where the focus is cleaner, antibiotic-free production and healthier water. For a farmer, the takeaway is narrower and simpler as to just treat packaging as a feed-quality variable you can specify, the same way you already specify protein.
Frequently asked questions
Is the feed bag really shedding plastic into my feed?
Partly. The evidence is circumstantial but consistent: every major study names packaging as a main source, and the dominant polymers in feed (PP and PE) are what sacks, liners and ropes are made from. What no study has done is separate the bag’s share from the fishmeal’s. Treat it as one controllable input, not the whole cause.
How much microplastic is in commercial aquafeed?
In the tilapia feeds tested by Siddique et al. (2025), 600 to 2,150 particles per kilogram, with every sample contaminated. Fishmeal sampled globally ranged from zero to 526.7 particles per kilogram (Gündoğdu et al., 2021). Levels vary by mill, ingredient and country.
Will this measurably cut my harvest?
The pooled evidence says microplastic exposure significantly inhibits growth and survival (Wang et al., 2024). How much depends on polymer type, particle size, dose and exposure time, and low-dose trials do not always show a growth loss. Read it as a real and cumulative drag on FCR rather than a fixed percentage you can plug into a spreadsheet.
What can I do about it this season?
Store sacks off abrasive surfaces and out of direct sun, since UV and friction both speed up fragmentation. Do not drag, re-use or repurpose feed sacks around the pond, and cut them open cleanly rather than tearing. Then ask your feed supplier what their packaging and mill contamination controls actually are and the question alone changes behaviour.
References
Gündoğdu, S., Eroldoğan, O. T., Evliyaoğlu, E., Turchini, G. M., & Wu, X. G. (2021). Fish out, plastic in: Global pattern of plastics in commercial fishmeal. Aquaculture, 534, 736316. https://doi.org/10.1016/j.aquaculture.2020.736316
Mohsen, M., Lin, J., Lu, K., Wang, L., & Zhang, C. (2024). Microplastic pollution in aquafeed of diverse aquaculture animals. Heliyon, 10, Article e37370. https://doi.org/10.1016/j.heliyon.2024.e37370
Siddique, M. A. M., Tahsin, T., & Das, K. (2025). Microplastic contamination in commercial tilapia feeds: Lessons from a developing country. Aquaculture International, 33(3), Article 190. https://doi.org/10.1007/s10499-025-01877-1
Wang, J., Wu, F., Dong, S., Wang, X., Ai, S., Liu, Z., & Wang, X. (2024). Meta-analysis of the effects of microplastic on fish: Insights into growth, survival, reproduction, oxidative stress, and gut microbiota diversity. Water Research, 267, 122493. https://doi.org/10.1016/j.watres.2024.122493
