Study summary · Bettas · Insect protein · Controlled feeding trial
A promising protein ingredient, with a formulation-specific result
In a 60-day feeding experiment, juvenile bettas receiving a formulated diet containing 13% black soldier fly larvae meal reached a higher average final weight than fish receiving the control diet. Higher inclusion levels did not produce better growth. This supports further investigation of insect meal in betta food, but does not establish a universal feeding level or a benefit for other fish species.
Why this study matters
Insect meal can replace some fish meal in formulated fish foods. The useful question is whether a particular finished diet performs well in the intended species, rather than whether an ingredient sounds natural or sustainable.
How the study worked
Participants
Sixty two-month-old Siamese fighting fish (Betta splendens), initially about 1.1 g, were studied in Malaysia. There were 30 indoor tanks, with two fish per tank and six tanks per diet. The six tanks, rather than all individual fish, are the relevant diet-level replicates. This was controlled tank research, not a trial in home aquariums.
What happened?
Five pelleted diets contained 0%, 6.5%, 13%, 19.5% or 24.5% dried black soldier fly larvae meal (Hermetia illucens). Fish meal declined from 31% in the control to 6.5% in the highest-insect diet. The 13% insect-meal diet contained 18% fish meal. Fish received the diets for 60 days. These percentages describe the complete experimental formulation, not instructions for adding insects to an existing food.
The comparison
The control contained 31% fish meal and no black soldier fly meal. Other ingredients included soybean meal, wheat, rice bran, molasses and a vitamin/mineral premix. The experiment compared complete diets, not isolated insect protein against an otherwise unrestricted household diet.
What was measured?
Growth, survival, feed-use measures, pellet properties, blood measurements and gut/liver tissue findings. Blood and tissue measurements used smaller subsamples than the full feeding population.
What the researchers found
| Outcome | Reported result | How to read it |
|---|---|---|
| Final body weight | 3.952 ± 0.042 g with 13% insect meal; 2.885 ± 0.220 g in controls. The paper reports a significant difference. | A result for this formulation and juvenile bettas. |
| Higher insect-meal levels | Final weight was 2.712 g at 19.5% and 2.307 g at 24.5% inclusion. | More insect meal was not consistently better. |
| Survival | No statistically significant difference among diet groups. | The experiment does not show a survival benefit. |
| Blood and tissue findings | Several blood and gut/liver measures differed. | These are indirect measures, not proof of disease prevention. |
Species and setting: Betta splendens · Freshwater · Controlled indoor aquarium/laboratory study. Broader relevance to other fish remains untested.
Related ingredient
What strengthens the evidence?
The study tested an ornamental species directly, used a fish-meal control and several insect-meal levels, and included six replicate tanks per diet. It reported the diet formulation and combined growth measurements with feed and tissue assessments.
What limits the conclusions?
This was one small, 60-day experiment in juvenile bettas using one source and processing method for insect meal. Random allocation and blinded outcome assessment were not clearly described in the inspected methods. Some feed/growth reporting is inconsistent, including differing variation estimates for feed conversion in the table and narrative. Blood markers and tissue appearance do not establish disease resistance, longevity or lifelong nutritional adequacy. Findings should not be generalised to goldfish, koi or every insect-based food.
What the researchers concluded
The authors favoured the diet containing 13% black soldier fly meal under their experimental conditions and considered the ingredient a potential partial substitute for fish meal.
Evidence.pet interpretation
This is directly relevant preliminary evidence for a processed insect ingredient in formulated betta food. The observed result belongs to the whole tested diet. It is not a recommendation to make 13% of a pet betta’s meals larvae, and it does not establish that insect-based foods are inherently superior. Growth is one outcome; a suitable finished food also needs to meet the animal’s wider nutritional needs. The study housing and feeding protocol should not be treated as a home-care guide.
Funding and author interests
The authors declared no conflicts of interest. No specific funding award was identified in the inspected acknowledgment text, which names collaborating institutions. This does not establish that the study was unfunded or independently replicated.
Read the original research
Kari ZA et al. Effect of Fish Meal Substitution with Black Soldier Fly (Hermetia illucens) on Growth Performance, Feed Stability, Blood Biochemistry, and Liver and Gut Morphology of Siamese Fighting Fish (Betta splendens). Aquaculture Nutrition. 2023;2023:6676953. doi:10.1155/2023/6676953.
Evidence.pet editorial summary · Study ID STU-015 · Source checked 23 September 2026. Strengths, limitations and interpretation are our editorial assessment, not a formal evidence grade.
Adapted from Kari et al. (2023), an open-access article under a Creative Commons Attribution licence. Evidence.pet has condensed the source and added its own interpretation.
Creative Commons Attribution 4.0 licence. The source has been condensed and reorganised.