You could feed fish fillet-fed cichlids to your predatory fish exclusively, but they will probably hold lower nutritional quality in them since they mainly consist of just protein, and some fats, trace vitamins, and minerals. I mean, sure, the fish fillets aren't that bad at all.. definitely a bit step up from protein flakes and pellets. You can possibly get away with just feeding fillets; but thing is, like duanes said, it's not complete. You also would want the fish belly meat, brain, eyes areas which are good sources of fats (omega 3's), and organs is a good source of vitamin a and d, etc. Your fish may not grow and live to their fullest potential if you just feed the same fillets all the time. They become malnourished. It's important to have everything covered for proper growth, development, reproduction, and repair. You know what I mean? So yeah, it depends on the different types and kinds of fish too. Some are way fattier than others, while some are quite lean depending other their diets. There needs to be a balance, just saying.
Plant matter could help address some important nutrients that are low/missing in fish fillets for sure and also gotta provide a bit more protein if the fish naturally eats a lot of smaller fish, crustaceans, etc in their native habitats. More vegetables than meat if the fish are herbivorous. Look up their natural diet.
Best to choose wild-caught fish meat if you can, by the way. Avoid fish from fish farms cause they are likely contaminated with a bunch of toxins, antibiotics, PCBs, and heavy metals unless labelled on packages stating otherwise. Even some wild caught fish are also contaminated sadly, tuna, swordfish, etc.. so do your research! You have to be cautious. WC fish is worth it in the long run, in my opinion. Better nutrition for health and longevity.
So yeah try mixing in some vegetables (go for organic, if you can) into your DIY fish food mix. Use other cuts of fish meats, organs besides fillet. Blanch vegetables (especailly if they're terrestrial) them so it's easier for fish to digest and helps remove antinutrients. Or feed fresh every now and then for the vitamin C content and enzymes. Or perhaps incorporate spirulina powder in the meat mix. Get creative.
I noticed when I feed homemade, DIY fish food to my fish, their colors pop and they become more colorful, healthier, growth is unregulated, they're more social, their activity level is off the roof, and their true behavior personalities awake. Throw in some probiotics too to help out their microbiome. Boom. You'll be even more amazed. I will no longer go back to flakes, pellets anymore haha maybe I'll throw some in on rare occasions along with freeze-dried/dehydrated foods.
All in all, when it comes down to it, provide lots of variety and many different foods when feeding your fish, toffee. Feed the cichlids a lot of different foods and they'll contain a lot more nutrition in their flesh and organs for your predatory fish. So I don't think just fish fillets is gonna cut it. Variation is the important thing. Don't just go feeding anything though! Food sources have to be whole, preferably from lakes, rivers, oceans, etc and less from land; whatever grows/lives in water or on water. Definitely should be eating diets that is similar and closely resembles their habitat diet as much as possible.
Hope this helps.
DIY Homemade fish food, for the win! Wooo hoo!
May I ask why use cichlids as a live fish food though lol. Live food action to get the predatory fish stimulated I'm assuming?? Gotta be a reason.
Have a good one.
Cheers.
