Scientists tested whether the material used to grow mealworms affects their nutritional value for farmed fish. They compared mealworms grown on regular commercial substrate with mealworms grown on leftover mushroom farming waste. Both types were added to rainbow trout feed at different amounts. The study found that both mealworm types worked similarly well in fish diets, boosting certain immune and protective systems in the fish without causing problems. This suggests that using mushroom waste to grow mealworms could be an environmentally friendly way to produce sustainable fish food.
The Quick Take
- What they studied: Whether the material used to grow mealworms changes how healthy they are as fish food, and whether fish fed mealworms stay healthy
- Who participated: Young rainbow trout were fed different diets containing either regular mealworms or mealworms grown on mushroom farming waste, compared to a control group with no mealworms
- Key finding: Both types of mealworms improved certain health markers in the fish (like immune system activity and antioxidant protection), and there were no harmful effects from either type
- What it means for you: If you eat farmed fish, this research suggests that using mealworms as fish feed is safe and healthy. Using mushroom waste to grow mealworms could also help reduce farming waste, though more research is needed to confirm long-term benefits
The Research Details
Researchers conducted two types of experiments. First, they tested mealworm extracts in laboratory dishes to see how they affected bacteria and protective molecules. Second, they fed young rainbow trout five different diets: a control diet with no mealworms, and four diets with either regular mealworms or mushroom-waste-grown mealworms at two different amounts (12.5% or 25% of the total feed). They then measured various health markers in the fish’s blood and organs to see how the different diets affected them.
The study compared mealworms grown on commercial substrate (the standard way) with mealworms grown on spent mushroom substrate (SMS), which is the leftover material from mushroom farming. This comparison was important because it tested whether using agricultural waste could work as well as traditional methods.
This research approach matters because it tests whether sustainable farming practices (using mushroom waste) can produce equally nutritious fish feed without sacrificing fish health. By measuring multiple health markers in the fish, the researchers could see the full picture of how different mealworm types affected the animals, not just one narrow measure
The study included laboratory testing before feeding trials, which strengthens the findings. The researchers measured multiple health markers rather than just one, giving a more complete picture. However, the specific number of fish used wasn’t clearly stated in the abstract, and the study was relatively short-term, so long-term effects remain unknown
What the Results Show
Both types of mealworms—regular and mushroom-waste-grown—produced similar beneficial effects in the fish. When fish ate 25% mealworm meal (either type), they had higher levels of hemoglobin, which is important for carrying oxygen in the blood. Both mealworm types also reduced lactate levels in the blood, suggesting the fish weren’t as stressed.
The mealworms boosted the fish’s natural defense systems in different ways depending on the amount fed. Lower amounts (12.5%) of regular mealworms increased an important protective enzyme called catalase in the liver. Higher amounts (25%) of mushroom-waste mealworms increased another protective enzyme called glutathione S-transferase in the intestines.
In laboratory tests, both mealworm types showed similar ability to reduce inflammation, though they differed slightly in their antioxidant power (ability to fight cellular damage). Both types also affected the growth of helpful and harmful bacteria differently, but in similar overall patterns.
Fish fed the higher amount of mealworms (25%) had increased cholesterol levels compared to the control group. The complement pathway, which is part of the immune system, was less active in fish fed higher amounts of mealworms. These changes weren’t harmful—they’re normal variations in fish physiology—but they show that mealworm inclusion does affect multiple body systems
This research builds on growing interest in using insects like mealworms as sustainable alternatives to fish meal in aquaculture. Previous studies suggested mealworms could work as fish food, but this is one of the first to systematically compare different growing methods and their effects on fish health. The findings align with other research showing that insect-based feeds can support fish immune function
The study doesn’t specify exactly how many fish were used, making it harder to judge statistical reliability. The research was conducted over a relatively short time period, so we don’t know if benefits or any negative effects would appear over months or years. The study only tested one fish species (rainbow trout), so results may not apply to other farmed fish. Additionally, the study measured health markers but didn’t track actual fish growth rates or final weight gain, which are important practical measures
The Bottom Line
Based on this research, using mealworms as part of fish feed appears safe and may offer health benefits (moderate confidence). Using mushroom-waste-grown mealworms works about as well as regular mealworms, making it a promising sustainable option (moderate confidence). However, more long-term studies are needed before making large-scale changes to fish farming practices
Fish farmers and aquaculture companies should pay attention to this research as it suggests a sustainable way to produce fish feed. Consumers who eat farmed fish may care because it could lead to more environmentally friendly farming. Environmental advocates interested in reducing agricultural waste should find this relevant. However, people with fish allergies or those avoiding farmed fish for other reasons don’t need to change their habits based on this study
The health changes measured in this study appeared within the duration of the feeding trial (timeline not specified in abstract, but likely weeks to months). However, whether these changes lead to better-tasting fish, faster growth, or long-term health improvements would require longer studies
Want to Apply This Research?
- If tracking sustainable food choices, users could log ‘farmed fish meals’ and note the source when available, tracking how often they choose fish from farms using insect-based feeds versus traditional feeds
- Users interested in sustainable eating could set a goal to research and choose farmed fish products from suppliers using insect-based or alternative feeds, then track purchases to monitor progress toward more sustainable seafood choices
- Over 3-6 months, track the percentage of farmed fish purchases from suppliers using sustainable feed practices, gradually increasing the proportion as more products become available in local markets
This research is preliminary and was conducted in controlled laboratory and farm settings. While the findings suggest mealworms are safe and potentially beneficial as fish feed, this study does not provide medical advice for humans. If you have concerns about the safety or sustainability of farmed fish you consume, consult with a nutritionist or environmental expert. This research has not yet been peer-reviewed (publication date is March 2026) and findings may change based on additional research. Always consult healthcare providers before making dietary changes based on aquaculture research.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.