I think in a few years most manufacturers will be using
insect protein of some sort, I know commercial fishers in Scotland are starting to breed black fly on a industrial scale
I wouldn't be so certain of that. Some perhaps, but I don't think most. Other novel sources of protein have most come and gone, such as pea protein. For the same reason as other terrestrial based plants, it's inclusion rate is limited when feeding fish. These novel sources of protein are specifically designed to lower feed costs, by reducing and/or replacing fish protein. But at the end of the day, nothing truly replaces the protein, fat, and growth enhancing substances found in fish. As always, what will drive the pet trade market will be what consumers demand, and what they are willing to pay. With regards to feeding fish, seafood such as fish, krill, etc will always be nutritionally superior, but at some point in the future the cost of those ingredients may outweigh their nutrient profile with some portions of this hobby.
When presented using names such as "bug bites" the purists believe they are feeding insects (Black Soldier Fly) to their fish, when in reality they are feeding BSF larvae, along with a mix of potatoes. peas, wheat, etc. The nutritional composition of BSF larvae depend at least partially on the composition of their feeding medium, so what those larvae are fed on the BSF farm will partially reflect what their nutritional profile is. Obviously this will vary, as will the maximum inclusion rate in feed among various fish species. See below:
www.mdpi.com/2304-8158/6/10/91/pdf
"BSFL meal and oil are already considered to be an animal-grade alternative to fish meal and fish oil used to feed carnivorous fish and in other animal diets, due to their high protein and lipid contents
even when fed plant-based waste streams [65]. The importance of fish meal and oil in aquaculture is well known, but competition with demands for fish for human consumption and depleted fisheries,
among other factors, have brought the supplies of fish meal and oil down and costs up, leading fisheries to search for alternatives such as vegetable oils [66]. BSFL can accumulate lipids in their bodies if fed an appropriately lipid-rich diet, and are generally more palatable to the fish than vegetable oils. Omega-3 fatty-acid-enhanced pre-pupae are produced when the larval diet is supplemented with fish offal [67]. Such “enriched” pre-pupae are suitable fish foods, producing no significant differences
in fish growth and vision development when compared to normal fish meal for feeding the rainbow trout, Oncorhynchus mykiss [68]. Sensory analysis of trout fillets found no differences among fish fed
fish meal, BSFL, or enriched BSFL diets [68]. Another case in rainbow trout recommended defatted BSFL supplementation in the diet of up to 40% without any negative effects on fish physiology or
fillet physical quality, but noted a decrease in desirable polyunsaturated fats [69]. Another study on rainbow trout placed the limit at 15% BSFL in the diet for unaffected fish growth [70]. A study on juvenile Jian carp (Cyprinus carpio var. Jian) found no difference between BSFL oil and soybean oil on growth performance, but decreased carp lipid deposition as the proportion of BSFL oil in the diet increased [66]. In the case of the turbot, Psetta maxima, although BSFL meals had relatively
low palatability and nutritive value, the use of BSFL was still recommended as a feasible, partial replacement for fish meal because it was reared on local greenhouse wastes [65]. Experiments with
African catfish, Clarias gariepinus, found total BSFL substitution of fish meal in diets (where it made up only 25%) had no effect in terms of growth rate and nutrient utilization indices, so BSFL were recommended as an alternative due to their lower cost [71]. Ultimately BSFL’s ability to efficiently produce protein-rich edible biomass from potentially protein-poor organic wastes has led many authors to conclude that BSFL can contribute meaningfully to sustainable aquaculture as partial or total meal
replacement [72–74], including for aquatic invertebrates such as shrimp [75]. BSFL has also been used in poultry feed as a partial replacement for maize or soy"
For commercial fisheries this makes sense, where feed costs can make up as much as 40% of a farms operating costs, but for the average hobbyist with only a few glass boxes, and who plans on keeping their fish for several years, or longer, looking to spare costs isn't typically on the same level as a large scale commercial operation. That, and there is almost no data to support the optimum inclusion rate with ornamental species of fish. I think at this point at best BSFL can be a partial replacement to fish meal. The key will be to pay attention to what follows the "main" ingredient in these foods, so as they are not just a low cost filler feed, with a dash of BFSL.
