lol and I had the almost exact opposite response from my fish.. theyw ouldn't touch tilapia but went straight for the smelt... imo whatever is the freshes/quality fish you can get is the best choice to feed. ideally leave the heads on innards intact, alot of nutrition in the brains and guts.
I haven't given up trying. My dumb self bought 10 kilos of small 3" - 4" (frozen) smelt and another 10 kilos of frozen sand lances (eels).
Very little likes the smelt and well at least my Morays and Tire track eel liked the lances and I was able to finally after a year finish the lances.
Like Amy stated though, if you are able to find a cost effective fresh supply of feed that your fish take to stay with it. I was also the biggest proponent of organ and brain meat. I have the benefit of being on the coast, and having access to many fresh fish markets and the historic Lexington Market.
Please be advised of one major drawback to feeding organ and brain. It is (IMO) a magnitude higher in leaving a film on the glass of aquariums than the "cleaned" fillets often "tailored" to human consumption.
It is much healthier to go with organ and brain, but it requires far more effort insofar as keeping the glass clean and water "polished" in a glass aquarium environment.
It was a no brainer when I was running under 15 tanks. Now that I am approaching 30 I have found myself getting lazy and forcing clean fillets onto my predators.